The problem with sales taxes - which we do have in the UK, VAT @20% - is that they're highly regressive. i.e. the people earning the least (pensioners, low wage workers) end up paying a much bigger share of their income than those at the top of the pile - the richest pay very little sales tax as a proportion of their income. As a result, the poor stay poor, and the rich get ever richer. And assuming we don't want the poorest to literally starve, we end up subsidising their costs with welfare benefits, social housing, etc etc - which have to be paid for somehow, and the middle classes don't have fancy tax accountants to move their money out of the reach of the taxman, as the wealthy and corporations do.
So you keep the poor poor, hollow out the middle classes, and the wealthy get ever more wealthy at a faster rate than anyone else. They then buy media companies, news companies et al to promote their views and systems, such as those that channel ever more amounts of money via companies into their own pockets via government subsidy (check out much money Walmart, and by extension the Walton family make from social assistance costs for their workers for just one example, or similarly amazon). They even end up becoming politicians and sponsoring politicians to sponsor laws that benefit them directly.
The correct answers are:
a) make companies pay a living wage, instead of making up the difference with subsidies
b) make companies and the wealthy pay their share of taxes instead of letting them continuously decrease it, because they benefit from a functional and well ordered society (educated and healthy workers, good transport, reliable infrastructure etc etc) more than anyone, they just don't want to pay for it
c) stop the vast amount of 'soft' money going into politics and media ownership as in any other circumstance it would be called bribery and corruption.
'Flat' sales taxes benefit the wealthiest the most. They are not the answer.