just to put another spin on it…
the inverse side of this question was recently discussed, around sitters’ concern that cancellations can (currently) negatively impact their account, even when the cancellation is for a legitimate reason:
Maybe a feature like the one you’ve described would be valuable if it also allowed the sitter to state why they canceled in each instance. That would help separate sitters canceling for legitimate reasons from those who are just flaky/unreliable.