No, trust me, once someone gets the first row, they don't leave it. Not even a millimeter. *bleh The only reason I took VIPs a few times (which were like 10$ more expensive than the regular tickets) was to be in the front and it was worth it.
Of course you're still allowed to go sit if you prefer that, it's fine. But the fact so many people like this atmosphere of being "squished like sardines" (which in fact doesn't even happen so often) means there is something enjoyable in it.
Yes, there is something special about it, because not only your sight and hearing senses are stimulated, but also your sense of touch with the proximity to other people, much less smell and taste. Even visually, you are much closer, the confettis fall on you, you call feel the heat of the pyros on your face, you can sing, dance, jump, whatever alone or with other people, great feelings. In the first row, you have a special connection with the artist(s), they can see you. Being in the crowd, preferably quite close, is just a totally different experience than sitting.
Sure, sometimes it's annoying and not cool at all, but it's not happened to me very often and I suspect had something to do with my foul mood to begin with. I did sit on a few concerts, but they're usually not my favourites, clearly.