I am trying to answer that. >people can agree on a minimum set of things. Agreeing on larger sets is nearly impossible. Spam on Bitcoin is like hate speech in real life. If you ban it conclusively (In the consensus / The Constitution) you go in the direction of censorship. And Bitcoin is permissionless censorship resistant money. OP_RETURN default of 42 Bytes is like saying we discourage hate speech / spam on Bitcoin. OP_RETURN default of 100 000 Bytes is like saying we encourage spam on Bitcoin / hate speech.