Why can't you stay in a hotel outside and take pictures in your room at night?

There is no such regulation in general hotels.

After check-in, the contract is formed. During the contract period, the right to use the house belongs to you-you can do whatever you want in the room as long as it doesn't violate the national and hotel regulations.

Almost all hotels have no rules prohibiting filming in the room.

But if you use the hotel to shoot movies and TV series, it is a special case, because it will affect other guests, and the hotel must agree and cooperate-if such a crew is shooting, you won't ask such questions.