Troi is kind of interesting in that the majority of her duties on the ship would be off-screen. She's meant to be overseeing the counseling department for the whole crew and their families. That's a lot of hours of couch conversation with people not spent on the bridge on the off-chance they encounter something she might be helpful for.
Remember, most ship counselors aren't actually empathic so they wouldn't lurk on the bridge. It wasn't until about season 6 or 7 that she actually got qualified to be a bridge officer, and that's when she started wearing a uniform most episodes.
For other random history:
Hardback Books Would Not Exist Without Cheese - Media Chomp
A fun tour on how it is the combination of cheese, snails, Jesus, underwear, and spectacles that we have the hardback book....