I was trying to figure out the same thing and I put it down to two things. First is the sentimental value and second is a lot of 8 bit and 16 bit games have editors that allow you to create your own game so people get hooked on doing something like that.
The style is also pretty popular, simplistic, and doesn't take up as much memory, so many 8-bit or pixel/retro games have much more room to edit, make a bigger game, focus more memory on music, add more features, etc. And sometimes, they're just so simple, they're addictive. And with the evolution of color throughout gaming years, there is so much more you can do in terms of graphics, even fooling the eyesight with levels of depth and detail since modern games no longer have to stick just to the 8- 16- or 32-bits of color limitations. Personally, I'm a fan of pixel games. Not meaning I don't appreciate life-like or even cartoony, 3d graphics. It all depends on the game and the level of charm. Hell, you can make a game terrifying with pixel art (Lone Survivor on Steam. Psychologically invigorating game, I recommend it.) Or you can make something very immersive on an emotional level like Undertale (Yes, I'm Undertale trash).
In short, I guess to each their own, but I can see why pixel games are very enjoyed still.
Maybe the fun is in the limits. You know you can't do this or that so you make the best of it kind of like the difference between playing with a Hot Wheels car and a radio controlled one. We know which one is better but Hot Wheels has an appeal of its own. What a lame example right? *laugh*.
Coming from a gamer's perspective, I would say it definitely has a more nostalgic history with us gamers. For most, it's the simplicity of 8bit and 16bit games. For some, it's the creative possibility that draws them.
I personally tend to ho that way because of all of the above. But that's just a gamer speaking his mind.
I think some of it is the fact that they are playing 'classics' as far as Role-playing Games are concerned. It's kind of like watching Gilligan's Island and old Star Trek flicks. The are clunky, but they are classics too.