The main reason to have higher rates of tax for higher earners is that everyone will require a minimum amount for essentials (food, accommodation, heating, travel etc). Once those requirements are met and people are earning many times the amount needed for essentials, then a higher tax rate will not significantly impact their quality of life.
In support of the above, to my mind the nil tax band should be set as high as possible to assist those on low pay. But an observation on State benefits for the poorer in our society; this subsidies companies who are able to pay minimum wage, which would otherwise not be a wage on which it was possible to live. But weaning working people off benefits and forcing employers to pay a reasonable salary does not help the mega-rich who are benefiting from our subsidised low wage economy.