Git is one (egregious) example though; Do I need to understand the fundamentals of every tool that I use/interact with every day? That's just not feasible. If not, where do you draw the line? To many, git is a means to an end, in the same way that $(insert_internal_tool_here) is. Nobody expects you to know the details of a B-tree and an R-tree to use MySql, so why is it ok to expect people understand the implementation details of git to use centralized version control?