I have a money-saving plan. I'm going to watch two movies at the theater even though I only paid for one.
Why wouldn't you just pay for both?
I'm trying to save money.
You need to buy a ticket for both movies. They may ban you from returning to the theater if they find you watching one of the movies without a ticket. That's the same as stealing.
Who's being hurt? They're showing the movie whether I take up a seat or not.
If everyone did that, a lot of people would be hurt: the actors, producer and film crew trying to recoup their investment as well as the movie theater itself. Just like everything else, it you can't afford something, it's wrong to just go out and steal it.