I created an account on www.zcash-wallet.org because I needed an address to transfer my mined coins.
This is what I get after my account is created:
Personal address to receive Zcash:
So that is my personal address they say.
If you look up that address you will see so many inactive miners and also transactions (https://zcash.flypool.org/miners/t1Ng4anC9YxZSxn5HCktCeG4ooTaSaQWkt6)
I was paying attention for a couple of minutes and the number of workers is always changing. I believe that some other people get trapped and they start mining without realizing that the address is not theirs.