Hope you're feeling better

When you tell someone that you're home sick the default reply here seems to be "Hope you're feeling better".

Is it just me or is that weird? Better than what? I just told you two seconds ago and you say you hope I'm feeling better. Better than two seconds ago? No, it's pretty much the same.

It makes sense to me if there's been some time since they learned that I'm not feeling well, since it's actually possible for me to feel better now than then.

First contact with the UK health system: 15min waiting for doctor in the emergency care thing (I'm not yet registered with a GP so I had to go there). The doctor examined me and gave me antibiotics (no trip to pharmacy required).

Didn't have to pay anything, and they didn't even ask for my NI number or proof of address, or ID.

To register with a GP I'd need to have two forms of ID, of which one would be a proof of address. I didn't do that since I didn't have any proof of address on me.

So in short: Why don't people say "hope you feel better soon"? Is it just that it's an automatic (but often incorrect, such as in my case) thing you say to someone who's sick, or is it idiomatic?