It helps them to release sexual energy. Humans are... Animalistic... By nature, so to be able to do something like rip a girl's shirt off, well... It's hot to them, makes them feel powerful and such. And who doesn't like boobs?
Why Do Boys Like To Rip Off Girls Shirts While Having Sex?
It makes them feel strong and they like what is under the shirt
Okay questions like these need to stay off.