I assume you're talking about why reqwest is necessary (i.e. why hyper is moving to async), rather than the single paragraph mentioning asynchronicity as a poss

I assume you're talking about why reqwest is necessary (i.e. why hyper is moving to async), rather than the single paragraph mentioning asynchronicity as a possible future direction for reqwest? Async I/O is important for more than just multiplexing a million requests. Hyper is moving to it for that purpose, and also because it is a more natural way for working with in-flight I/O, e.g. cancelling requests or selecting over them.