Vegeta's far more intelligent than most give him credit for. Just because he doesn't understand and can't really relate to human culture doesn't mean that he's not smart. He's a brilliant strategist and tactician, and is good at watching and waiting, even when he's impatiently doing so. Although it was done under Frieza's orders, Vegeta's assisted in the conquering and destruction of numerous worlds. There was more to taking over a planet than blowing things up. You had to get to know your enemy first, and that meant observing them.

As far as he was concerned, watching this movie was his attempt at further understanding an alien culture that he was fully immersed in. Might as well, since it was looking more and more like he'd be stuck on this Kami-forsaken rock for a while.

"Unlikely. I'd kill them before they managed to take anything."