It’s stealing because you watched it. If you didn’t watch it and didn’t buy it or steal it, then nothing has been stolen. The entire crux is that you’re consuming and ingesting the product they’re selling without paying for it.

Additionally, if you’re making the argument that you can’t count “potential” sales of something as theft then you can’t also make the argument that “potential” exposure is valid. Either both potentials are valid or neither is and, if they both are, then it’s theft.

And you’ve just proven my argument for me with your art gallery examples. Art galleries explicitly give people that access. You pay for that access. If you don’t pay for it, you don’t get to look at those paintings without buying anything because you already had to buy something to even get to look at the paintings. Unless the creator is explicitly giving you access for free, you’re stealing if you’re ingesting or consuming something that they made for which they are charging.