"Why do we wait to check in until the tests are done?"
All too often, we take these questions as a suggestion that we change our behavior. "Why don't you foo?" is something we take as "Do foo." "Why do we do bar?" is a question we take as "Don't do bar."
But it is a question, not a directive.
Sometimes the correct response really is, "No good reason. Let's change that." Sometimes, though, there is a reason why we do things. Maybe we don't test X because we're getting rid of that feature, or we don't have the hardware to do it. Maybe we do wait to check in until the tests are done to make sure our coverage stays high and we don't create technical debt.
Answer the question. Then change your behavior - but only if that's the right answer to the question.