They're trying to encourage use cases that would otherwise take up memory and leveldb storage to instead use OP_RETURN, which is preferable for making nodes still runnable on commodity hardware.

They did this because they have no idea how how to fix arbitrary data insertion prpblem that they facilitated with segwit+taproot.

It's like that episode of Rick and Morty, where Rick invents a love serum that ends up rewriting the genetic code of the entire planet to be sexually attracted to Morty, requiring further fixes to the human genetic code, over and over, until humanity is a formless pile of goop.