Imagine you need to change the type that's passed to a function. You attempt to update all places, but you miss a path that's in an edge case. Static typing wo

Imagine you need to change the type that's passed to a function. You attempt to update all places, but you miss a path that's in an edge case. Static typing would have caught that for you. By waiting until runtime, you've now just potentially shipped a regression. As a code base gets large, it's just not possible/practical to run all possible ways the code you're editing can be reached. Unless you happen to be lucky enough to have 100% unit test coverage, which very few people do, and running that test suite is somehow quick enough to be a practical alternative to static typing.