They're*
Well, as I said before : Every gang is different. They have different protocols for what to do with the money.
When I used to lead a gang, my rules were : if you took money out of cartel, leave a 5% percentage in gang bank. Its easier done with what is currently put in place. We wont change it just because a few people want it. Also, Leaders can be money hungry. I know a few that make you put the money in and end up using it for their personnal use.