Just wanted to add something here, since I work behind the pharmacy counter at a Boots store...
The reason we ask you all the questions when you try to buy something from behind the counter is because we're told to.
The the till screen even has prompts for us:
What is it?
Who is it for?
How long have they had the symptoms?
Are they taking any other medication?
You guys get the third degree because we have to cover our backs. We need to make sure we give you the correct product for your symptoms and if we don't check, and accidentally end up selling you something that could actually make the symptoms worse, we can get into big trouble.
For example, I might have someone come in and ask for a chesty cough medicine, but when I ask them what their symptoms here, it turns out that they don't have a chesty cough at all (it might be a dry cough instead) and giving them what they originally asked for is not actually going to help them get better!
It's the same as the 'Do you have an Advantage card?' question. People get fed up with being asked these questions every time they shop in Boots, but that's what we're trained to do and if we don't ask, we get in trouble with our managers.