Groovy sucks, no clue about Grails, and tomcat is utterly horrible. ^.^;
You’d never really had an issue where you accidentally passed a {:ok, something} to a function instead of a something? Or wanted to have a restricted set of inputs to a certain function that would not accept anything else and enforce the caller to verify it is correct before, say, blindly passing in user input? Or etc… etc… etc…? Type systems are awesome as they categorically prevent all those issues and far far far more. 
Tomcat is not only slow but by default is very open and can be taken over with ease (locking it down is a first step of any install of it, and it is easy to miss a lot of vectors). But the container api for java is pretty well standard so you can literally take the server you have no and replace tomcat with a better one and it should all still ‘just work’ (usually). 
Er, yes! ^.^;
Not just a little faster either, it is a magnitude of difference. But yeah not an issue if serving up to a few a second, but getting more than that and PHP can still survive where even well crafted Ruby/Rails apps will fail.
Even then it is common in a lot of languages (either built-in or via template-new-project-systems). ^.^
