They don’t save me from having to go look at other files to learn things about the code I’m actually interested in; they can be misleading in ways that types aren’t—in particular, it’s very hard to know what sorts of things an all-green test suite guarantees versus a passing static type build, without a great deal more information; and they are, in practice, prone to rot and neglect in a way static types rarely are, and are harder to bring back into a useful state when that happens.

They serve very different purposes and generally are not first and foremost good communication tools the way static types are, for a bunch of reasons. That doesn’t mean tests aren’t very useful and welcome things to have, however.