1. Async allows you to parallelise tasks. If a request from a user needs to hit three logically independent endpoints, you don't need to do that in sequence, yo

1. Async allows you to parallelise tasks. If a request from a user needs to hit three logically independent endpoints, you don't need to do that in sequence, you can do them in parallel and thus the user will get a response much quicker. 2. OS threads can be expensive in the sense that they can block a lot of memory, to the point where you could run out of threads at some point. This is worse in some environments than in others. Apart from async, another solution for this is virtual / green threads (as in Erlang, Haskell, and much more recently, Java). 3. Some async implementations enable advanced structured concurrency patterns, such as cancellation, backpressure handling, etc.