Do you mind telling us why wouldn't you join one?
All crews are like countries. They don't like each other. They cannot team up properly nor do they have a good plan. They do not use voice chat to communicate so there's no point joining one.
And if all crews were one, with better plans with voice chat, no criminals would complain about cops. So, there's no point playing with people by joining a crew, if they do not use voice chat at least.