While Photoshop is a very powerful tool, it is by no means the only tool involved in producing a high quality photo, nor the most important one. Photography is a crap in/crap out type of art form. You can't achieve a good end result by taking crap in to Photoshop and somehow expecting it to magically allow you to fix what is inherently broken.
Photography is a complex and deep field. Achieving a great photo requires taking a good photo, with an artistic vision (which godfatherofpolka's answer describes well) and intent for how you want it to come out. What angle should the photo be taken from, what lens should be used, what lighting should be altered? This and countless other questions are key to having a good starting point from which to work.
So, fine, lets assume we have a great photo to start with, why do the filters still not match the results achieved by someone skilled in Photoshop? It continues to be a matter of artistic vision and skill. Filters apply a general pattern to an image, but really good application of effects to an image requires careful customization to the way the image looks to start. Just using a basic filter is a bit like trying to paint the Mona Lisa with a spray paint can that only comes in one color. You might get something that is recognizable as an imitation of the Mona Lisa, but won't get much further than that.
Really getting the look requires careful control of how the image is manipulated and painstakingly tweaking it to fit the desired aesthetic. There is no magical button to do this quickly and most likely it took the original photographer a decent amount of time to produce the look as well. It is often possible to determine the basic adjustments that were made, but the art work of it is in the fine tuning and that is going to be unique on a per photo basis, so even knowing exactly what the photographer did won't help much if you don't have a similar level of skill.
So in short, the key issue is that photography, both the capture and the manipulation is an art form. You need to be skilled in each to fine tune an image. A great photograph makes it look deceptively easy, but 9 time out of 10, it takes a lot of skill and effort to really achieve that look you are hoping to emulate.