Because you'd typically have to collude to do it. If just one company did this, anyone being charged more would switch to the other company. You'd have to have some kind of agreement among all the competitors to do it, or build it into law.
Some mobile games with in-app purchases do various flavors of this, but it's more based on willingness / capability to pay than affluence. And of course they're structured such that switching to a competitor would make everything you've previously paid in moot.
> Because you'd typically have to collude to do it
There's all sorts of ways that companies charge the wealthy more for the same product without collusion.
1. Coupons
2. Generic brands that are repackaged name brands
> anyone being charged more would switch to the other company
And this is a common way to charge the wealthy more for the same product. Someone making $500K+ is less likely switch ISPs every year, or even spend the time to threaten their ISP they are going to switch.
That's doing it by proxy, though, and isn't what I took OP's question to mean. S/he specifically mentioned a comparison to income tax, which is much more direct.
Some mobile games with in-app purchases do various flavors of this, but it's more based on willingness / capability to pay than affluence. And of course they're structured such that switching to a competitor would make everything you've previously paid in moot.