I think it's more of an anti-stupid thing. Where I am, pharmacists will often talk to you about each first-time prescription, describing when and how often to

I think it's more of an anti-stupid thing. Where I am, pharmacists will often talk to you about each first-time prescription, describing when and how often to take pills. You don't get that via non-prescription, so dosage control is a hacky fix for people that won't read labels. It's also "smallest person" thing. If you're 2M tall and muscular (eg, more mass), your dose isn't the same as a 160cm person with little mass. The doses are for the smaller person, for safety.