It reads like you think progressive taxation is not bracketed. Which is something often found with people from poor background. Let's say you have some system

It reads like you think progressive taxation is not bracketed. Which is something often found with people from poor background. Let's say you have some system where your taxed 0% for income < $20k, 10% between $20k and $40k and 30% for $40k+. You currently earn $39k. You have to pay 10% of $19k so $1900, you keep $37.1k after tax. You're offered a $2k raise. Lot of poor people think that you'll suddenly have to pay 30% * $41k so $12k and lose money. But the 30% is only applied to the portion of revenue you get over $40k. With your raise you know have to pay 10% of $20k + 30% of $1k so $2.3k so you keep $38.7k after taxes, so your raise end up being $1.6k. You have not lost anything. Now the problem comes from social benefits which usually are not regressive and work on a all or nothing system.