~50% of people are capable of using it while standing, that doesn't mean all want to. I've heard a fair number of men rag on men who won't sit on their own toilet and splash piss everywhere, since it just makes a mess you have to clean up. So the math is actually tipped more in favor of sitters, who make up a non-zero proportion of people who are able to pee while standing, plus everyone who's obligated to pee while sitting.
I think it's weird to care about lifting the lid, but leaving it up shows you left it open while it flushed and that's kinda gross to a lot of people.