using trapdoors for aesthetic means for buildings, like as an accent or a structural part of something. if they're used as the occasional table/shelf its ok, but i see them used everywhere for a lot of little architectural flourishes
server has this weirdness with them where they just tend to open on their own
or if you right click them once accidentally and close them back up again they'll reopen back to when they were open and you have to mine them and repeatedly place them until they stay put