[nemetroid]

It sounds very reasonable to me. I would say 90% of programs don’t need threads or concurrency at all.

[hot_gril]

Anything that waits on I/O needs concurrency (but not necessarily threads). Web backends, web frontends, deeper backends, desktop GUIs, that's probably 90% of software right there.

[sealeck]

Rust is a systems programming language though.

[hot_gril]

I interpreted the 99% thing as referring to all software. If it's just Rust projects then sure, then again anyone who needs async has probably been avoiding a language that lacked async until recently.