>>319004362
because you haven't looked into what's in there, that's all it is. 
Live concerts, live djs, insane visual effects, general party atmosphere, and it's like 4ch, refresh and there's more. 
You literally never run out of things to do. With the exception of high level or focused vr games like Pavlov, HL:A, sims like racing or flight or elite, no man's sky, and a few other stand-outs everything else you could ever want to see and do in vr is in vrchat. 
Plus you get to be and look like whatever the fuck you want. 
Why do people enjoy interacting with others in mundane places like bars to play overpriced pool on a shitty table? 
Why do hundreds of thousands to millions of people fork out huge money for EDM festivals and raves?
Why do people do any of those things? Sometimes it's about socializing, sometimes it's about dancing, sometimes it's about playing pool, or cards, or chess, or mahjong, or entertaining others, or being entertained, or exploring places you couldn't go in real life, going to a haunted house or riding skateboards or motorcycles or shooting missiles out of a jet at each other without the overhead of an 80$ game nobody else plays. Or to chill on the couch and watch a pirated movie or anime together with friends. People do this shit on discord already, this is just better.
And the voice chat is honestly one of the best of any game, somehow. Probably because that's priority #2 after avatar tools for the devs.

Basically VRChat's servers have 35,000 people in them on the weekend and you can do literally ANYTHING YOU WANT, and nearly everything is possible at potato graphics or full on realtime lighting and reflections. 
That's why. The playerbase and fuckhuge creator base makes this game a non-stop deluge of awesome vr shit to do. 

If it wasn't vrchat it would be some other social vr game with great tools. Maybe Cluster.MU or AMBR eventually, who knows.