Income tax is cumbersome, open to fraud (and, consequently, necessitating intricate anti-fraud bureaucracy) and tends to depress economic activity.
While it is true that VAT and other indirect taxes tend to land heavier on the poor rather than the relatively rich or affluent, this perceived unfairness can be ameliorated via a generous benefit system and, also by the use of variable rates of indirect tax. In other words, a luxury item such as a Ferrari might be taxed at up to or beyond 100% of its base value, whereas items such as tins of food might attract a rate of, perhaps, only a few percent. Some items, notably water and bread, might be exampted altogether.