Well, for one thing, the tax system has changed about 375 times since then.
...For another, in most of the intermediate incarnations, in most realms, the Ruler ended up being pretty darn poor. If he split his income to the rest of the Council, he'd have practically nothing.
If you give the ruler control with no minimum, he simply not pay them if he doesn't want to because it lessens his income too much, though I don't know of any realms that the ruler makes less than 300 gold a week.
