Tabs vs spaces, braces on the line above or a line by themselves, allowing implicit true/false vs requiring a leading 0 != in c/c++, function naming conventions, documentation system conventions, etc., etc. Sure, you could quit every time you disagreed with any of those decisions, but that seems like a lot of wasted effort and time. For all of those, I could disagree and commit to working collaboratively on the team that had made a decision other than the one I preferred.