Correct, at the moment, we assume the depth of the recursion is fine by default which in my opinion is a dangerous default. If you know/assume the depth of the recursion to be small, then it is probably worth to be explicit about it. For example, it will make it much easier to discuss in code reviews. And if it is a warning, then it is easy to disable it locally, globally or even turn it into an error.
I am not necessarily proposing to verify each recursive function is tail-recursive by default. The compiler would only to verify a function call itself.