It would be to much work. Since xptminer tends to be for a specific coin, and can only be used for their site. He have to make a new version of every coin someone wants to mine. He'd have an easier time setting up his own altcoin pool and charging a fee
Well there are 2 ways - either you hardcode the pool, or you hardcode the fee address. A hardcoded fee address going to cbuchner1 would of course mean that he needs to have his own specific address for each new coin... well but that's doable, isn't it?