One example is by the innovation of technology. We now have antibiotic regimens (like Z-Pak) that only consist of 6 pills, over 5 days and packaged in a way that’s clear what to take and when. This makes sticking to the regimen and following through much easier than a 30 day course.
But, if these class of medications became available OTC, how many people are going to buy 30 pills which cost ~$10, over Z-Pak which cost ~$50?
Also of the population at large, it’s hard to know what percentage of these are going to be more frugal, and/or less educated on the matter, since 1) They’re not seeing a doctor, and 2) even general education isn’t mandatory or equal.