The scenario is that the host (mostly) only opens the other door when s/he wants you to switch (because s/he knows that you have selected the "car" door). If you have selected a "goat" door, then the host (mostly) does something other than open one of the doors and offer you the chance to pick again.

It's a bit of stretch to interpret the question this way, of course, and doing so makes the problem rather strange so I find it quite clear that this interpretation was not what was intended.

Note that the question didn't clearly state that the car can't be moved after you've picked, that the goats aren't extremely valuable nor that the car isn't a cheap toy, that you actually "win" what is behind the door you select, or any number of other possibilities that make rather little sense. So I don't get why these alternate routes are so compelling to consider.