Corruption thrives in the dark spaces. Everyone thinks that the income tax code is about income taxes. It's not. It's about creating ways for government representatives to get bribes for creating various wealth protection and amplification schemes. They call it "Job creation", or "Progressiveness", or "The Economy, Stupid!", but the whole scheme was created by wealthy people for wealthy people who don't think poor people are good for anything except extracting wealth from the dirt.

Sales tax is up front. It is paid anonymously. It shows people what things should really cost. Income tax hides everyone's actual labor value behind paywalls, paperwork and various schemes so that they don't know what they have to bargain with. It hides the profits of corporations so they don't know what they are bargaining against. It allows corporations to deduct the cost of brainwashing children from their income taxes.

Sales tax is less regressive than a dead planet.