"Can I ask you a question?"

This is a question that I've found myself asking and it's been annoying me, simply because it doesn't make any sense - it's a stupid thing to ask!

Why? Well, it doesn't really give the person that you're asking much choice, does it? Your asking for permission to ask a question ... by asking a question? How's the other person supposed to say no?! By anticipating the question and interrupting you?! One person at a place I used to work would always respond to this question with: "What? In addition to this one or is that it?" - which made me realise the error of my ways ... except it hasn't stopped me repeating the mistake!

It just seems to me to be a natural way to check it's alright to interrupt someone when you want to ask them about something. Stopping asking this is probably not a change that's going to revolutionise my life, but it's a habit I want to break because it's a stupid thing to say!