1) Cuz I got no upper body strength. 2) I've always found it mind numbingly boring.
I've been doing crossfit for the last 6 weeks and we do a lot of weights, amongst other things. It's amazing how much form makes a difference, in addition to the fact that good form is actually quite hard. Fortunately for me, crossfit adds just the right amount of variety to make it interesting. And painful, in a good way.