There's a ton of overlap with the people that stop taking antibiotics once they feel better rather than finishing the course (and thus have them sitting around, and decide to take them the next time anything at all is wrong). In some cases doctors will also relent and just write a "get out of my face" prescription to shut a hypochondriac up, but that's more rare these days because most realize how bad an idea that is (in the past, it was considered fairly harmless to prescribe a course of antibiotics even if someone didn't need it, but now we mostly know better).