For girls, it's a part of the so-called feminine mystique: what is socially-acceptable for women to do and men are expected to tolerate. Not vice-versa, of course.
Let me lift the veil on what this process really is.
It's when the woman "arbitrarily" changes her mind. In reality she becomes unsure and decides to not even show up. Cue whatever lame excuse she desires.
There is another way of putting this: she turns chickenshit. (There is a proactive form of it when she doesn't even agree to show in the first place. This can be a surprise to the uninitiated man.)
Don't forget to call women out on it.
This PSA pleasantly brought to you by BlackPoisonSoul.