I did consider that but I didn't have a good view of them from my seat. So that would mean I would have to stand outside of it for a good ten minutes to be fairly sure it wasn't in use before performing what (who knows) could be an illegal action. Anyway, as someone has pointed out to me before, a metal tube hurtling through the sky is not a good place to cultivate possible conflicts.

I would rather that they didn't keep the lavatories locked the whole flight OR explain why they're going to be locked the whole flight. Sometimes there is a good reason to lock a lavatory for the whole flight, apparently.