I don’t know why we ever bother to leave the ship.
Why, indeed, is it that the Doctor and his companions leave the safe (usually) confines of the TARDIS every time they jaunt, unguided, through time and space, other than the fact that there wouldn’t be much of a show without this reckless behavior? Barbara asks this very question at the beginning of Peter R. Newman’s “The Sensorites” (Story Production Code G), spurring the companions to reel off all of their extra-TARDIAL adventures to date: pre-historic earth, the Daleks, Marco Polo, Marinus, and the Aztecs. And the Doctor replies, “It all started out as a mild curiosity in the junkyard and now it’s turned out to be quite a great spirit of adventure.”
“The Sensorites,” alas, is one adventure our fearless travellers would have been better off just staying in the TARDIS for. They certainly try, for as soon as they leave the TARDIS and see that they’ve materialized inside a spaceship crewed by two seemingly-dead humans, the Doctor himself is keen to get right out of there. The first ten minutes of the story seem like an apology for the plot to come, with each character in turn suggesting that they get right back in the TARDIS and leave, but as soon as you see Susan lock the TARDIS door, you just know they’re getting locked out.
By these guys, no less:
In fairness, Howe and Walker make a good point about the story’s attempt to portray an alien culture with, well, alienness and in a subtle and sympathetic vein. But the real interest for Doctor Who fans is in the continued development of the companions and the early stirrings of canonicity.