They won't give it up at all, because there's absolutely no reason for them to. The reason they have this power is because they wield force legitimately, not because fiat is special.
Many that have studied this system would disagree.
Most income taxes collected in the US/UK go directly to these private organizations.
In many ways slavery in the US was 'abolished' in 1865 then a revised version (aka perpetual debt slavery) was adopted in 1913 at the tail end of the US-China opium trade induced economic boom and expanded by both parties in the decades that followed.