One reason is the management of the AGM. With say 400 members and a 25% quorum, you have to get a hundred people (or more) in one place within a very fixed time frame.
The default quorum is 10% (or 10 people, whichever is greater) and I think a 40 person AGM is perfectly doable.
Also governance issues, in that everybody must understand their responsibilities and liabilities.
Calls for an EGM could happen from time to time as well.
So how would you choose which applications to accept?