I agree that sitting would be nice. I feel kind of funny standing on the Captain's Chair on my Bridge or standing on top of a table in a lounge ready to be social. Either that or give my female Vulcan a Table Dance Emote !
if you read the Engineering Report, the Devs have explained that while a "click to sit in chairs" function is in the works, it has been set aside to work on more vital graphical problems. in the meantime, you can sit on any chair by first jumping up and standing where you want to sit, then using a sitting emote.
To be frank, while it is a pain in the butt to have to do that, I don't really mind, it's not a game breaker to me.