I agree. Managing many http requests or responses was a motivating problem.

What I question is whether 1. Most programs resemble that, so that they make it an invasive feature of every general purpose language. 2. Whether programmers are making a conscious choice because they ruled out the perf overhead of the simpler model we have by default.

That is why we have the function colouring problem and a split ecosystem in the first place - if it were obviously better in all cases, we'd make async the default, and get rid of the split altogether (and there are languages, like Erlang, that fall on this side of the fence)