The miners are accepting these out of band payments because they are bringing in more fees then on chain transactions. If pools do not share those OOB fees to miners, miners will eventually catch on and move pools.

As real financial transactions start to increase on chain, people will be willing to pay higher fees forcing "inscriptors" to keep up or stop. Although, I may not agree with it, we're seeing a free market in action right now. It's not always going to play out the way we want but the incentives behind #bitcoin should help to keep everyone honest and the network healthy.