Type errors can happen in small programs. In ML applications, which are computationally very expensive and take a lot of time to run, an avoidable type error can result in a considerable waste of time.

Type annotations can be useful in helping a reader get a rough outline at a glance, of what some unfamiliar piece of code is doing. Especially under heavy use of broadcasting.

The second is compactness is true only if you're chaining straightforward library calls. If you're writing your own functions or building non-trivial functionality on top, types will be of aid too.