To me it seems as though alot of guitarists listen to music to listen to how hard it is to play it. Like to be able to say wow these guys are effing good. Anyone can play fast, just alternate pick and hit random frets quick, easy. Writing is the hard part. To me, to be able to put the right emotion into music is the hard part, not making yourself look like a guitar god, I know who I am and I know Im good at guitar, not to sound cocky. I know alot of guitarist who are amazing at guitar but cant write for crap, and barely care to learn theory. To me getting good was the easy part. Playing alot will make anyone better. It took alot of time to learn how to write, it takes alot more, I memorized a bunch of scales and modes, and learned how to use them and make them sound good.
I found writing to be easier than getting my chops up. The thing is though that most people don't really understand the whole part of putting emotion into music, or about having slow or melodic music. I love to play slowly and just close my eyes and feel the music, you know?
I think when people listen to difficult-to-play guitar music, they listen to it because they feel it improves them. At least, that's why I listen to it so much. The main reason is so I can listen to a lot of good guitar playing and imitate their insanity until I can make it sound as easy as they do. Speed is always an important part of certain genres, but I agree with you in the sense that dynamics are very important.