can only be used for their site
You realize you're talking about ypool, right?
yes, and Ypool miner only works with Ypool

and they have their own coins too... (or very close too..) which sounds pretty far away from any ideal behind crypto...
My point is the miner has to customized for each coin. that is a lot of work. So, anytime a coin is added. a new version has to be made. as I said..easier to make a mining pool with a fee.