OK, how would you feel if the person who owned your apartment before you came in with a key he still had while you were out and sat in your bedroom in the dark (not using power) playing with himself?
You're not using your flat, it's there anyway, you've not lost anything, nothing has been broken or damaged, he's gone before you're back so it's fine right?
This is more a question of privacy than of "stealing"/"not paying". In a world where privacy didn't exist (i.e. there would be no "reasonable expectations of privacy", I wouldn't mind.
Let's use another example. I order food, but don't eat all I get. If you will eat it, I would be very glad, as it wouldn't go to waste.
Why is your expectation of a right to privacy an issue but not the creators expectation of payment for their work?
After all, at the time they created it the legal and commercial framework, as well as the social norms, said that they could expect payment from anyone who consumed their work.
Why are you allowed to override their expectations yet someone using your property without your permission isn't allowed to override yours?
You're not using your flat, it's there anyway, you've not lost anything, nothing has been broken or damaged, he's gone before you're back so it's fine right?