D&D Campaign Disbandment Survey

Most D&D campaigns don't end with a final battle… they just… stop.
I'm working on a future discussion for the channel and I need your help: In all the D&D games you've played, what's been the number one reason the game ended or the party fell apart?
1.What do you think is the number one reason a D&D game you played in ended or the party fell apart?
2.Have you experienced multiple D&D sessions ending for the same reason?
3.Which campaign setting did you last play in when a game ended?
4.How many players were typically in your D&D games?
5.How frequently did your group play before the game ended?