Why do tax brackets work this way why is it that a Rich/Wealthy person the first few 000 dollars may be taxed?

Do you covet your neighbors husband ? How about their car? This class war crap is pure Marxx BS. What is my incentive to do anything if your going to take 3/4 of my earnings? Just move to CUBA. They have no rich at all. They took 100% of the wealth.