I agree that -w is still useful if that's what you really want and you are willing to accept the consequences. However, I've seen that in many, many cases, it is used out of ancient habit even when it's not the most appropriate. Using it together with warnings shows some of this confusion: if you want global warnings you just need -w, and if you want lexical warnings you just need warnings. If you use both, it's because you don't know what you want, or you don't understand the difference.

(Note, here "you" is used as a generic pronoun, not refering to any specific person).