February 5, 2009 6:27 PM GMT
Hi--
Bridge from Star Trek to Star Wars. It's the same set of answers, really.
The easy answer for why they'd always use Class-M (Oxygen) planets: cost-effectiveness.
Think about it: a breathing device isn't cheap, can give out at a moment's notice (based on the need to advance the plot), and to find intelligent life on a class-J (gas-giant) or class-O (mostly water, little/no land) planet might be tough. (Although you can make the same argument about the life on Earth, I suppose.)
Plus, it saves the fx dept a wad of cash not having to create a new enviro-suit
and all the aliens can have two functional legs, as opposed to say, fins.
Just my two quatloos worth....
Peace and Long Life,
Mina Sakura
(Who looks
hot in a Star Trek Original Series women's uniform)