The whole point is that use of async doesn't need to be infectious. You may want to make everything async for elegance and consistency, but it's not a requireme

The whole point is that use of async doesn't need to be infectious. You may want to make everything async for elegance and consistency, but it's not a requirement strong enough to cause problems. If you have a library that is sync-only, it's fine. If you have a large project and can't be bothered to rewrite everything to be async, it's fine. "Not everybody knows (how to do) that" is a weak argument, because it's a relatively straightforward thing to learn: if it can block, wrap it in `spawn_blocking()`.