I’m watching “Enterprise” and Capt. Archer is staying on a paradise planet in a small apartment. With a door.
Why do you think all alien civilisations have doors in science-fiction? Would they all have arrived at the same concepts of territory, property and privacy that we have?
Petafloptimism 
Just part and parcel of the Star Trek Universe…
Ever notice how everyone “evolves” except the Native people? Modern primitives indeed 😉
Climb that ladder!
Gosh.
Would you believe it, they even have corridors… Chob(n)in Klingon.
http://www.kli.org/tlh/newwords.html
You obviously missed the Next Generation episode when they explained why most of the galaxy has taken to the anthropomorphic form.
If the galaxy was ‘seeded’ with the genetic blue print to make lifeforms group with two arms, and two legs — it’s reasonable to think that their brains would evolve in a similar fashion as well and independently decide that doors would be a good idea.
I saw the same episode, but my question was — with all these people jumping into bed with aliens, isn’t it more likely that an alien might have a hideously disgusting way of having sex?