I think that most people who call Psak Halacha Hotlines do not have their own Rav to call, or it’s a question they are not comfortable asking someone who might know who they are. I know the second one happens because I did that once.
Personally, I wouldn’t recommend calling a hotline unless it’s for something very basic or unless you know who the Rav is answering the phone and he’s someone you would be comfortable asking a sheilah to in general.