The problem lies in your last point. Any PHP+Apache app, no matter how bad the programming practices, has the property that every request gets a blank slate except for explicit database connection. In most other stacks it is way too easy to add a singleton class or a global variable and break that guarantee.

That said, I'll gladly take the guarantees of a type checker in exchange for giving up the guarantees of statelessness. It would be nice if there were a stack that could give me both.