The reason why more coordinators are not popping up, I have already asked that question here (somewhere). Apparently, you need so much initial capital to start with - for example, the ~6000 seized Chipmixer bitcoins would be enough - and most people who want to run a coordinator just don't have that kind of money.
You don't need any capital to start a coordinator, liquidity comes from the users. 50 inputs is an estimated lower bound for a WabiSabi coinjoin to provide a consistent amount of matching outputs.
That is 50 inputs of reasonably large vales - obviously I can't just load 50 0.01
BTC inputs and expect user with 1
BTC to get their input properly anonymized.
The reason I said lots of capital (we are talking at least $1,000,000 if you want several 0.1
BTC inputs) is necessary in the first place is because you can technically feed users coins without having any of your own, however, those coins will
not be mixed. (
https://eprint.iacr.org/2021/206.pdf, change outputs). One would have to have a couple of 0.01
BTC, 0.1
BTC, 1
BTC inputs and so on, because the protocol relies on randomly returning an input from the anonymity set for he coinjoin process to truly give you privacy.