This comes from confusing 2 different notions of reward. I don’t find the notion of cracking open my brain to wirehead my reward terribly appealing. Sure, I can predict that I would experience vast reward if I did.
My current mind forms an imaginary mental model of the world where I wirehead, and the world where I don’t. My current mind, which hasn’t yet been wireheaded compares those worlds. My current mind can consider any consequences of wireheading I think relevant. “If I wireheaded, my cat would starve. I really like my cat, so I won’t wirehead” is a perfectly valid argument. Your current untampered mind is imagining a future. That imagined future contains a wireheaded you, and a starving cat. Your current mind judges this whole imaginary world as bad, and does something else instead.