In that case, we can't trust people to take the medication in the first place, even with a prescription.
No, we can't, not fully. Drug addicts and ignorant folk who don't finish their antibiotic course because they "feel better" on day 6 of 10 are part (yes, part, not all) of the reason we have resistant bacteria.
But since we do, we can at least establish that they're generally more prepared than the non-consenting animals, right?
Not really, no. My friend's college buddy died because he ignored the "only do one trial at a time" mandate and the drugs interacted, fatally. As it turns out, people who get paid to take experimental drugs are more risk-tolerant, to the point of danger, than most people. They're not more prepared, rather more desperate for money.