Except that the gain in this case in realm-wide, while the cost is very much local. The realm has great incentives to accept new knights all the time, but the ones who can actually offer them oaths, the lords themselves, don't. The gain on estates is marginal, so they are just throwing their gold away out of charity.
Your knights don't aid you agendas? I recommend you get some new knights cause mine are MOST helpful in furthering my ambitions. The more knights I have, the less work I need to do to sway other nobles into my camp.
