Sometimes it feels like people talk about this sync/async issue in a vacuum. But often there is a real need to get a response from the recipient in a timely manner. You can't just sit around twiddling your thumbs waiting for a response hours later because until then you might be blocked.

It isn't just the big things that could block you. A small piece of feedback, an opinion on a design decision, a review of your approach etc all require relatively quick and synchronous responses or you end up in multi-hour or multi-day long chain of async discussions. Business can't move at that speed.