The normal talking point (not taking sides here) is disposable income; this is a bit of simlification, but hopefully it illustrates the idea well enough.
There's a lot of people on low incomes that live paycheque to paycheque. They literally pay rent (or mortgage, if they're luckier), food, heat and light and that's their paycheque gone. Given the rush to minimum wage following its introduction (we saw the same thing in the UK) there's a significant number of people in that position.
Someone who's got a larger income typically has disposable (or excess, if you prefer) income above and beyond what they need to maintain their quality of life, and so a larger tax burden doesn't actually impact them in the same way as it does for the lower earners - a higher tax burden might delay some purchases, but doesn't generally cause real trouble.
For the very high earners - the minority we normally think of as 'rich' - the tax burden is almost irrelevant - they literally earn more money than they can spend, and what's not spent simply heaps up in a bank account somewhere. Bearing in mind that a higher tax burden here has almost literally no impact on their quality of life (as the extra money is just a number of a statement), it becomes more a question of 'why not?'.
Bear in mind that a lot of people in this last bracket are seen to give away huge sums in aid anyway, which makes it difficult for society to argue they can't afford it.