For a CRUD app, of course it doesn't make much sense and you'd probably have to be a masochist. :) But there are valid use cases I can think of: Anything that's very CPU intensive that would need to run very quickly: dynamic image generation, or something that does a complex series of operations on user input that needs to delivers the results ASAP.

Of course it's usually easier and safer to just throw more CPU at it, but at a certain scale that might get too expensive...