Because you're doing it wrong.

Well, it hurts.I think you're tearing my penis skin off.

Why are your hands made of sandpaper? It's a humid day. Do you want to use some of my moisturizer? I have a huge tub. I'm just saying.

I think I'm bleeding. Yup, the bottom of my shaft is bleeding. You can't see that blood? It's on your hand.

Can you spit on your hand or something?

No, I don't think it's gross.

You're not a tugboat. No tugging!

Ow. Owowowowowow. OW!

Okay, stop. I've got to go put a band-aid on my dick.

I, uh…I don't think we should see each other anymore.