There would be two ways to implement that, neither of which are particularly good. You could either have the exit function call itself from its __repr__ method, which an abstraction violation so egregious it introduces security vulnerabilities (imagine a logger printing repr(thing) to stderr, and someone sneaking the exit function in there for it to print), or you could special case it by making exit a reserved word, which flies in the face of the Python 3 ethos which changed print from a reserved word to a function and breaks a lot of established code.
Programming languages have rules that the programmer is expected to learn. Part of being a programmer is foregoing a certain amount of user friendliness in favor of an environment that is more powerful so that we can actually get things done. Programmers are paid to memorize and follow these rules so that the end user does not have to learn them.
Oh my God, where has this program been my entire life? I've been hackily using a Python interpreter to do back of napkin math and trying to keep track of units etc in my head (and making frequent use of the up arrow key when I need to save a result from a previous equation). This program would have been a game changer if I'd discovered it a few months earlier before I finished my university physics course. It probably still will be next semester. I'm sincerely blown away by the automatic unit conversion. Each variable has a unit, and when I divide joules by meters I get newtons. This is fantastic and I cannot believe it is free, much less open source!