I think at first it was because of a limitation of the cameras present at the time, but with the color cameras that we have available now, what do you think of black and white photos?
In other words, what does a photo being black and white visually suggest as opposed to the same picture in color?
I think there are subjects and shots that work much better in monochrome than in color. There are others that don't.
For pictures where the color itself is a major component of the picture (e.g., rainbows, sunsets) color is essentially always preferable.
In other cases, however, a monochrome image can can eliminate distractions and do a much better job of portraying the real essence of the shot. Just for one example, I find this is often true of portraits -- most of the color in such a case will be the people's clothes, so monochrome often helps emphasize the person over what they're wearing.
Do Ansel Adams' photos make sense today? Obviously they do. There are not many photographers who can produce color images of the Yosemite valley as good as Adams did in B&W.
Mostly, the choice of B&W is artistic, rather than technical. The link provided in the comments to the question suggests many of the considerations.
Sure, it does, and in some circles, it's still pretty popular. I just did a quick survey of the photos currently on exhibition on 1X.com, and there are around a dozen B&W (or monochrome) photos there out of 32 on that page. These guys tend to favor highly-processed fine art photos, but this still gives some idea that there's enough B&W photography going on that it's still relevant.
One difference with B&W today vs. "way back when" -- I'd bet that the overwhelming majority of these photos were shot in color (very likely RAW) and converted to B&W. The power of processing software like Photoshop and Lightroom provide you with some awesome tools to control how your photo is converted.
When I see B&W photos that work well, they tend to be fairly simple in one way or another -- maybe they've got a single subject (a person, for instance) or they show a scene that's dominated by a single color (a forest picture that's all shades of green). Good candidates also have a lot of contrast in them -- this contrast can stand out better in the photo when color is removed (think about how the colors in your scene can map to black, white, and grey).
Yes definitely.. people have their own reason why they do it. Ansel Adams was definitely the master of B&W. For more recent example check out Chase Jarvis' Seattle 100: http://s100.chasejarvis.com/
Personally I convert a picture to B&W when color is proving to be more a distraction or if it doesn't really contribute much to the theme of the picture..
This question is tagged "history" so, some history --
Photographs (of course) don't have to be literal captures of a scene. Plenty of photographers (past and present) have manipulated the image to reflect their feelings about the subject (or other stuff).
Pre-digital (and really, before desktop computer image editing -- which pre-dates pure digital photography by a bit), making color prints in the darkroom was tedious and the number of variables you had to control for using a limited number of tools you had made artistic exploration difficult. But with traditional B&W film photography, you had a wide number of tools (colored filters on the lens to change contrast, different contrast papers and all of the other darkroom techniques) and a limited number of variables in printing -- the exposure and the contrast curve for your single "color channel" (gray).
Also, by removing the color -- which humans have a good memory for in terms of what looks "right" -- you have more freedom to move away from a literal capture of the scene.
For color, a lot of people ended up preferring slides instead of prints, but it can be difficult to hang a slide in an art gallery. So color became less important in the art world.
Post-digital, there really aren't any limitations on what can be done with a color image and people have done some amazing exploration with HDR images, manipulating different color channels independently in different ways, etc. All of which are important additions to the creative toolbox.
But there is a huge history of B&W imagery in western culture, so there are still people interested in it. And sometimes a self-imposed limitation can be part of the creative process (like folks who just post the JPG files straight off the camera, without any post processing).
Under digital, it doesn't make sense to capture the data in black and white; that is to say, to shoot that way.
With film, it is usually a decision about how to capture the picture: you can use black and white film, and shoot in black and white. Yet, not necessarily. A color negative can be processed to black and white paper. Because that's not the same thing (black and white film has its own behaviors and nuances), there is a case to be made for shooting black and white: a certain type of film captures an image in a way that only that type of film can capture, and that is part of the art.
Since a digital camera has a color image sensor, if it allows black and white shooting, that's because software on the camera reduces the RGB image data to grayscale. It's probably better to shoot in color and then have control over the algorithm for doing this conversion, rather than leaving it in the hands of the camera firmware, unless it documents how it is done.
Converting to black and white is a tricky business. The main question is: which color model is used to determine the lightness of a pixel? For instance, we can convert RGB pixel values to the HSV color space, and then just take the V channel as a grayscale image. But this is not accurate. A pure, saturated blue color (#0000FF, in a common RGB notation) is darker than a pure red (#FF0000). Yet, the V value under HSV is the same. If the conversion to grayscale is based on the V from HSV, color will affect lightness in a way which is incorrect with regard to human perception.
A good way to convert to grayscale is to map the image to the LAB color space, and take the lightness channel as the source for the grayscale data. Not literally of course, because the L channel is logarithmic; rather, the A and B channels get obliterated to gray, and then the LAB values are recomposed to RGB. The LAB color space takes into account differences in brightness among the colors: the L channel is normalized accordingly.
If I cared about producing great B&W images, I would only rely on the camera if I was sure it was doing the conversion in a way that handles the perceived lightness of colors properly: either by using this LAB color space, or else, say, based on some function which emulates the behavior of black and white film (how its lightness is influenced by color).
