It's not work for the winner. For the winner, it's super-easy. You just send a letter saying "Give us gold or else." If the victor is the one doing the work, then you're doing it wrong.
And if the payments are late? If one needs to constantly nag every time to remind? If the realm is some time away, forcing delays between when the gold is collected and can be distributed? If the gold is too spread out and it takes time to gather the gold into the hands of a single person?
Threats are also meaningless if your army has moved on to other things. For many realms, simply re-mobilizing the forces back into war-mode is a challenge in itself.
There is also the 50 gold charge every time which ends up amounting to significant amounts.
