With async/await you can tell from the type signature whether a given function might suspend, and then reading through the body you can see whether each function call is a non-suspending one or a possibly-suspending one. It makes it really obvious what's doing what. If suspension is your only effect then it probably doesn't matter (one unmanaged effect is ok), but when you have other effects that might interact, having all the suspension points be explicit is really useful. https://glyph.twistedmatrix.com/2014/02/unyielding.html gives one example.