I found (2) blocks yesterday and I only have (4) piles of 200 dmd each. So staking is working as it should. I believe you just have to leave your wallet open to compete. If you close your wallet at all I believe it removes your chances of stakes. Also, if you freshly opened your wallet it will take some time to compete with all of the wallets that have been open.
Yes, I think people got used to the DMD wallet v 2.0 in which they could obtain a reward by running your wallet once a week for a couple of hours.
But with DMD version v 3.0 it works a differently.
Imagine that you have a mining farm which operates around the clock.
If you stop it, you will not receive income.
Same here, only the energy cost for launching the wallet is minimal.