If you want regular code and not async, then yes, it matters: if you have a lot of OS thread-based actors performing blocking network "send"s as part of their r

If you want regular code and not async, then yes, it matters: if you have a lot of OS thread-based actors performing blocking network "send"s as part of their regular control flow, each of them blocks an OS thread and you'll run out of resources soon. If those actors are backed by lightweight threads instead, which are very frugal, basically you are only limited by the network stack.