Giving everyone the same amount is symbolically useful, because it's a way in which all citizens are equal. Everyone gets the same amount and what can be fairer than that?

But, practically, anything a UBI plan gives you can be undone with an equal and opposite tax. The net effect after taxes is what matters and it's going to redistribute money or there's no point in doing it. Some people pay more taxes than others and raising the top income tax rate is enough to ensure that the wealthy don't benefit.

It can be made exactly equivalent to a negative income tax.