Is this default really that big of a problem? Most people running Tokio are going to be running it on multicore hardware, and they'll get some additional throughput for free. If they're sufficiently resource constrained to the degree that they realize that a single thread is a better fit for their domain, they'll Google it and realize you can use Tokio's single-threaded runtime.
To be clear: it is a one-line change to make Tokio use the current (single) thread.
Those Send + 'static bounds have really big impact. Multithread is definitely not just "additional throughput for free", nor is the change between single to multi just one line of code.
To be clear: it is a one-line change to make Tokio use the current (single) thread.
https://docs.rs/tokio-macros/latest/tokio_macros/attr.main.h...