This is why. You remember those badass USP .45's Angelina Jolie used in Tomb Raider? Yeah... she has real ones.
Here's the money quote:
"I bought original real guns of the type we used in Tomb Raider for security. If anybody comes into my home and tries to hurt my kids, I've no problem shooting them. Brad and I are not against having a gun in the house, and we do have one. And yes, I'd be able to use it if I had to."
Yeah baby. Yeah.