I think for me the coolest thing about Pink Floyd is how their songs are very theatrical and dramatic. Like they how they are able to tell a story, with twists and turns, but a lot of the time with very few lyrics, more instrumentation. I also like how laid back a lot of the music is, its perfect for putting in the background and doing some work.
I did listen to them a lot in high school with my friends, so there is some nostalgia and memories tied to it, but those experiences just add to it. It's still great music regardless.