Look, it's freezing outside. And just because dogs are 'technically' supposed to pee outside, doesn't mean they always want to go there.
Sometimes, it just feels better to wee-wee indoors, then pay the consequences -- whatever they may be.
In this video, a little pup looks anxiously outdoors as snow comes cascading down. He knows he's supposed to go outside, but he just ... can't. So he does what all dogs would do in this situation.