>if questions are only for r/askhistorians

You're literally in a thread designed for questions, so no, questions aren't only for askhistorians.

> then why is the main page always full of well questions?

It's not? (edit: went back, over the past 50 submissions allowed on the page only 5 of them are questions/discussions) There can be questions in the main page IF they follow the rules, these are much stricter than the ones allowed here, namely that they have to show prior research, an understanding of the historiography, a substantial write-up, and have a question capable of generating discussion. We require that because 99% of the time questions asked can be answered with a bit of research, and a bit of time.

Edit: I will add that sometimes we do send detailed questions to other subs because they are more likely to have the base of users that will be best to answer it. If you, for example, post here with a detailed question trying to understand a passage of ancient Greek text we'll suggest you take it to /r/AncientGreek because 99% of our users don't know any Greek and the comment thread will just be full of 300 quotes.