Very often questions (and, in particular, differing opinions as to the correct answers) hinge on whether the individual is native to the US, UK, or some other place on the globe. But only very rarely does the individual's profile identify place of residence and/or birth. I can appreciate that many people want to "retain an air of mystery", but isn't there some way to encourage them to at least identify their place of residence in their profile so that one doesn't have to repeatedly inquire?
I think there is some modest encouragement present already in user profiles: location is an item there. If a user leaves that field blank, well that may be an omission, but it is probably intentional with active, long-term users. I rather doubt any additional "encouragement" will work.
However, I do think people may be more specific than they currently are (overall) in what they're actually asking, via tagging. We do have tags for regional variants (and if we don't, we should). Tagging an individual question (in case regional variants matter, of course) is much more to the point than the location of the asker because a correct tag can specify what dialect/variant of English the question is about, rather then where the OP comes from. It is perfectly acceptable if a user from, say, Denmark asks about, say, Indian English: in that case, a tag helps, whilst location of the OP does not.
FWIW, one can always ask in comments. People may be slightly more willing to part with their personal info in comments, which are disposable and/or not immediately visible to your random profile viewer. Anyway, that information, if relevant, should be included in the question.