This is why MANY politicians do NOT want a flat tax. The ability to control all aspects of our lives rest in the tax code. It is evil above all and our number one problem. If people actually had one number that they could see in the payment of all their taxes they would first vomit, second they would revolt.
We are being held as slaves to a system that serves few on the backs of many and the elected are happy with it.
One of the most egregious and pathetic examples is the insistence the Social Security is in some bizarre way a 'Successful' program. Successful in what way? I never see any backup to these blind pronouncements. Medicare/Medicaid are other examples of Gov'ts zeal to control no matter the financial and social costs - As long as the control is maintained. IMO They will eventually swamp Social Security as examples of Gov't waste and corruption and in the not-too-distant future.
I could go on and om with examples but your illustration says it all - As a larger proportion of GDP falls under the purview of the Pols the amount of true freedom available to both payers and recipients decreases in direct relationship. Unfortunately, there appear to be too many individuals and entities who are self dealing the system to their own advantage and it is they who have the power. Therefore I don't see a reversal of this trend and in fact see just the opposite.
There seems to be a lot of support for the Value added tax, which might have some merit. The only thing I'd be leery of is the possible end to the cash system as a way of monitoring compliance. That would be even worse than we have now as there would be an ability by government to record and control every transaction that's made.