Because there are some people who want more for themselves, that's why. They recognise, to some extent, that that means less for other people.
And they don't care.
There's been several studies documenting that for most people, having way more than what's needed reduces their empathy for people who don't have enough to survive. It's a human brain problem. The solution is taxing the shit out of wealthy people so they don't become brain-damaged.
