[nyanpasu64]

I'd argue that libraries forcing programs to include an async runtime upfront because there's a chance that it may someday grow to the extent you want a central executor (when they are absolutely ill-suited for audio programming, and probably not the case for Animats's metaverse client at https://news.ycombinator.com/item?id=37437676), imposes unnecessary dependency bloat on applications. And unless you use block_on(), async code pushes applications from a "concurrency library" model where apps block on mutexes/signals/channels as needed, to a "concurrency framework" model where code only runs under the runtime's callbacks (which is not the right choice for all apps).