Yeah, after the inital "let's get down the front so I can touch his geetar and he can sweat on us" craziness of my youth, I've always wanted to be able to see the band, and concentrate on the band, in relative comfort.
Relactive comfort, for me, is not and never has been standing up for an hour and half on a sticky floor in the dark getting either a) jostled if I got too close to the stage, or b) bumped into by some drunken beer waiving nurk if I got too far back (and therefore too near the bar!). And the constant stream of idiots pushing past you and through you to get nearer or further back is SUCH a pain. And you just get comfy so you can just about see between heads without blocking the view of the less-vertically-endowed person behind you, and without nestling too close to the person next to you, and then some foul smelling tall prat pushes through you all and stops 5 inches right in front of you blocking your entire view with his stinking personage.
Also, I have no intention of dancing or jumping around when I can see the artiste, playing his/her stuff, right in front of me. I would much rather dance to the records. When the dude's doing his sh1t in front of me, I've kind of paid to watch every moment I can see. And dancing seems a waste of that opportunity... (but that's just me personally as a punter).
It does kind of feed into how I felt as a performer I spose - I didn't complain if they got up and danced near the end, but I was very happy having a room full of eyes watching my every move. I was kind of performing to be watched and listened to, not to be danced to etc.
So, yeah, I see what you (gwem) mean by "depends on the music". But... for me it depends more on whether the act is interesting to watch. If it's a got a guitarist or anything approaching a decent front-person then I want to watch and listen. Eg I've seen Motorhead I dunno, 4 or 5 times since 1980 or so. It was only the very last time a couple of years back that I didn't have seat. It was OK, nice to see the old boy etc, and they were superb... but I'd had a much better time in the previous gigs, sat down watching them, and then maybe jumping around on my seat for the last few songs...
EDIT: Fourth Feline posted his while I was doing mine. Yep, your description of gigging is my memory of it too. You could see what effect you were having on them emotionally. It was nice if you had a bit at the end when folks got up and boogied or whatever, you'd shared in the emotional experience and now you were sharing something physical. My experience of playing standing venues is that people concentrating on the music look awfully bored and not at all relaxed - not very good feedback for me as a performer. Put the same bunch in seats and they looked so much more into it.
Actually, early on, we were really p1ssed off that we couldn't get anyone to dance. One rehearsal the band asked me to stop doing what I did so much. I said "why?". It was because they'd spoken to some of the audience and found out why they weren't dancing. I said "and why is it?". "Because they say they'd rather watch you, and if they dance they think might miss something..." .... and that's how I go to see gigs myself.