Right now any new player has to decide if he wants to join a tribe or create one out of nothing by his own.
In the first case, he might be chased off, simply by finding his prefered tribe unused/ nonexistent.
In the second case, he will suffer from the game mechanics, that will kick him in the back after a couple of days.
Both cases might chase some players of.
Also the game suffers from that artificially reduced diversity.

Wouldn't we profit from the abandonment of the minimal requirements of numbers for a tribe?
Who would suffer from tribes inhabited by only one player p.e.?