Yes, the whole hoopla about async and particularly async/await has been a bit puzzling, to say the least.
Except for a few very special cases, it is perfectly fine to block on I/O. Operating systems have been heavily optimized to make synchronous I/O fast, and can also spare the threads to do this.
Certainly in client applications, where the amount of separate I/O that can be usefully accomplished is limited, far below any limits imposed by kernel threads.
Where it might make sense is servers with an insane number of connections, each with fairly low load, i.e. mostly idle, and even in server tasks quality of implementation appears to far outweigh whether the server is synchronous or asynchronous (see attempts to build web servers with Apple's GCD).
For lots of connections actually under load, you are going to run out of actual CPU and I/O capacity to serve those threads long before you run out of threads.
Which leaves the case of JavaScript being single threaded, which admittedly is a large special case, but no reason for other systems that are not so constrained to follow suit.
Except for a few very special cases, it is perfectly fine to block on I/O. Operating systems have been heavily optimized to make synchronous I/O fast, and can also spare the threads to do this.
Certainly in client applications, where the amount of separate I/O that can be usefully accomplished is limited, far below any limits imposed by kernel threads.
Where it might make sense is servers with an insane number of connections, each with fairly low load, i.e. mostly idle, and even in server tasks quality of implementation appears to far outweigh whether the server is synchronous or asynchronous (see attempts to build web servers with Apple's GCD).
For lots of connections actually under load, you are going to run out of actual CPU and I/O capacity to serve those threads long before you run out of threads.
Which leaves the case of JavaScript being single threaded, which admittedly is a large special case, but no reason for other systems that are not so constrained to follow suit.