I think it's a kind of tone adjustment. Looked at charitably, it's a way to "soften the blow" of disagreement by phrasing one's contradiction in a less less abs

I think it's a kind of tone adjustment. Looked at charitably, it's a way to "soften the blow" of disagreement by phrasing one's contradiction in a less less absolute or certain way. Looked at less charitably, it's a way to disagree and still leave room to walk away (accusing one's interlocutor of unjustified hostility) if backing up that disagreement becomes too inconvenient. Either way it's a bit of a hedge, kind of like "it seems to me" or "some might say" in slightly fancier clothes. Personally I find it a bit smug and tiresome.