I can grant you, it wasn't regular.
For 2 reasons, one I mentioned before, and they are related to each other:
1. Other to store data are cheaper
2. There was no economic demand to do this in OP_RETURN
No economic demand is the only scenario where filters work. If there is economic demand, filters do nothing
Now, it would actually be BETTER for the health of the network/noderunners If shitcoins/jpgs moved to use OP_RETURN instead of witness:
1. OP_RETURNs can be only up to 1mb, not 4mb
2. OP_RETURN consumes less resources than alternatives
3. Alternatives produce unspendable UTXOs, which grow UTXO set - the absolute worst outcome for node runners
So by preferring (because you cannot stop it) witness/inscriptions instead of OP_RETURN you choose a result that has 0 effect if there is any economic demand, but harms all node runners and the network much more than OP_RETURNs
So much for protecting node runners
