One of the difficulties of talking about general practices is there are so many variables when you consider all of us in the aggregate. There's the game we're playing, the campaign setting, individual group dynamics, and even our own individual points of view that need to be considered and few blanket statements will cover every situation. Everything might be potentially up for negotiation but that doesn't mean everything is in actuality.
My suggestion to players is this; If you're not onboard with the premise then speak about with the GM prior to introducing your character concept. If the GM tells you there won't be any Force users in the campaign, don't start by telling everybody you plan on making a Force user. The message it sends to the GM and the other players is your character is more important than the campaign everyone else wants to play. Talk first about the setting, then pitch your concept, and if the GM says no then gracefully accept it.