Why were disposable flashes prominent for so long?
Technology moved at a much slower pace back then, especially with regard to consumer cameras. For most of the 20th century, a camera was something you bought and used for decades. Even professionals, such as some of the photojournalist 'stringers' in my hometown, were using Speed Graphic types of cameras from the 1940s and 1950s as late as the 1970s!
For most of her life my mother used two cameras:
- A Brownie she got as a girl in the late 1940s when they were practically giving them away so people would have a need to buy film for them.
- A 126 Instamatic very similar to the one pictured in the question that she bought in the late 1960s and used well into the 1990s when cheap, easy to use compact 35mm point and shoots flooded the market.
In the last two decades or so she has used at least a couple of those 35mm compacts (that didn't last near as long as those first two cameras did before they stopped working) and at least four compact digital cameras over the last 12 years or so (that also were replaced due to no longer working properly). She only used two cameras in the first 50 years of taking photos, then at least six cameras in the last 20 years!
The consumer market back then was much more concerned with price than with technical performance of cameras. In a way this has come full circle, as most people today are happy enough with the results they can get with even fairly mediocre phone cameras that they're no longer buying consumer grade compact cameras that give much better image quality.
In the context of cost, one of the ways to enable the lowest possible price is to not put anything on the product that the consumer doesn't absolutely need to use it. This was the case with flash. Many, many people only took pictures in daylight and didn't need a flash at all. Flashbulbs and then later flashcards were pretty cheap relative to the increased cost of putting a built-in electronic flash in a camera. To add insult to injury, built in flashes consumed batteries at a rate that cost almost as much as the disposable flash cubes or cards did! It took a LOT of use of an electronic flash to offset the additional cost of the camera with one and the batteries to run it compared to the cost of using disposable flash.
Bear in mind that flashcubes and flashcards provided the energy for the flash from the chemical reaction in the bulb, not from a battery. A mechanical striker in the camera could produce enough current to trigger the flash without the need for high current batteries. Even the many cameras that did use batteries to trigger the disposable flash used miniscule amounts of battery energy per shot compared to a battery powered electronic flash.