> the industry obsession

Or maybe they haven't thought about it?

Or they tried some simple alternatives and didn't find clear benefits?

> The key is to give the agent not just the ability to pull things into context, but also remove from it.

But then you need rules to figure out what to remove. Which probably involves feeding the whole thing to a(nother?) model anyway, to do that fuzzy heuristic judgment of what's important and what's a distraction. And simply removing messages doesn't add any structure, you still just have a sequence of whatever remains.