Regular or Extra Strength?

Question of the day. Why do they make pain reliever medicine that is regular strength and those that are extra strength? Is there a market for regular strength pain meds? I mean, do some people say, ehhhh I think my headaches only so-so so I think I'll take a chance and regular it today. You would think it would be priced higher or something, but no. Do they sell more in general if there's a bottle of regular strength Tylenol next to the extra strength? For the record, if I am in bad enough shape to be at the store looking for pain meds, chances are I will not wing it on regular strength. Just a thought...