> Blocking off face-to-face time is a signal that the work is important enough to get done.

This.

I'd also add that not bothering to book a meeting means that people treat you like a low-value work queue that they use to dump low-visibility and low-accountability work. They invoke you to handle silly tasks that no one but you accept.

By requiring a meeting, you're increasing the threshold of effort that your requester is willing to invest in getting it done. If they can't be bothered doing a meeting, you shouldn't bother doing the work for them.