On at least ten occasions that I can think of over the last few years, I;ve been at the GP for myself or one of the children and been prescribed antibiotics for in a few days, just in case the problem hasn't resolved. "We don't usually prescribe antibiotics for this as it's usually viral, but I'll do you a prescription just in case it hasn't cleared up by next week" - that sort of thing.
I imagine that rather a lot of people, being ill and in possibly pain, will think "stuff waiting" and pick up the prescription on their way home to get started with it straight away. As I did on one occasion with a raging UTI that was so painful I couldn't face waiting another few days to see if it went by itself.
I can see exactly why GPs do this, of course. You can't tell a patient to come back in for another appointment in a few days time if they're still ill, when it takes weeks to get an appointment sometimes!
Still, this is a drop in the ocean compared to use in agriculture and in countries where you can just buy antibiotics over the counter, no questions asked.