Your pharmacist has sold your prescription data to some shady third party for advertising purposes. Somehow they managed to loophole that out of HIPAA - it's a 'service' for your own good - or something along those hallucinatory lines.
Supposedly you can opt out but you first have to know if you got opted in.
I'm actually surprised that this hasn't generated much flack, but there are so many things to get angsted at I think that most people are just overwhelmed. Personally, I ran out of extra angst a long time ago.