I ask this question because I do not understand why this pool is so popular if there are equal much cheaper pools.
I assume that many miners think that "When you hit a whole block, does it really matter if you give 2% vs 1% or even no fee at all?" , .
But then the answer to your question is rather difficult, Ck solo pool has been here for years, as it says in the title that it found 267 blocks so far, Kano's solo pool is relatively new, and as far as I know, no block was hit there yet, and you know it takes time for something new to be as popular.
Also, this pool requires no registration or login, you just use your BTC address which is pretty damn convenient.
Another reason could be "personal reasons" regarding the pools' owners themselves.
There are probably many other reasons, it's the same question as why many of us use Viabtc and pay 4% instead of using Poolin/Binance with only 2-2.5%, it's not just about the fees.