Locking it to the bike isn't a good solution if you live in a place where it rains or snows a lot. So you end up having to carry it with you on errands. If you

Locking it to the bike isn't a good solution if you live in a place where it rains or snows a lot. So you end up having to carry it with you on errands. If you bike a lot, those small inconveniences add up. I can't imagine fashion sense is much of a reason, that seems like a strawman argument commonly conjured up by helmet laws advocates.