I jsut did some digging and it seems you're right, it's only for methods which call themselves (which indeed get compiled into a loop, as an entirely local transformation). So not hugely useful.

Apologies, I've not written Scala for many years; I just recalled that there was a way to annotate tail calls which the compiler checks. I didn't realise it was so limited!

Scala is in the way to get capture checking for effects, which will allow to do RAII like stuff, or borrow checker like stuff for that matter.