Ask HN: Why no user-side filters in messaging apps?

This literally just occurred to me today after deleting and marking as spam the 999999999999999th fundraising text message from some political candidate. Email has had killfiles for decades. Yet Apple provides no way for users to, say, automatically delete anything on iMessage with the string "actblue." Neither, as far as I can discern, do other major messaging apps like WhatsApp, Facebook Messenger, etc.

Is this some kind of technical barrier? (I imagine it could be done client-side, so encryption isn't an issue.) Or an explainable product decision?