I already mentioned some examples how to disincentivize it. For instance, some privacy coins drastically reduce the amount of publicly viewable data per transaction due to encryption of many transaction components.
Here's a minor but important thing to note: those particular cryptocurrencies you mentioned previously didn't begin with this feature, which appeared a trouble for some later on. And even if they did, removing it later should be considered censorship. Second, as far as I understand, cryptocurrencies like grin and monero don't have the analog of OP_RETURN? Isn't that a serious disadvantage for forward compatibility?
bitcoin has always had rules to reject certain data/tx's..
I don't talk with people who don't agree with me on Bitcoin's most important principle being censorship resistance.