Yeah, as I see from Google Analytics, mostly people visit Bitcoin, Dogecoin and Ethereum faucets. Other coins like Blackcoin, Bitcore, Dash and others aren't popular, so I can't earn decent ref commission from these faucets.
And you can't use Google Adsense on faucets. Having quality content doesn't helps. Though, I'm not sure about faucet lists. Probably I can use it on my blog/faucet list, because I have quality original content. But I wouldn't risk to try, because I don't want to get ban.