I remember the days back when <frame> was still common, and I wouldn't call it good enough because of the way it interacted with URL and history. It was basically impossible to bookmark a specific page on a website that used frames.
It's a shame that was never solved because there is no reason it should be "impossible". Nowadays we have more control of URL and history. There must be a way.
Well, the way frames are specified, each has an URL in its own right, so the way to do it would be to come up with some algorithm that combines them all in a single URL without losing any data. The resulting URLs would inevitably be messy, though.
These days we basically hack around all this in JS by manually controlling history. Which is brittle as hell, and why so many web apps break "Back" etc.
Managing state is always a hard problem. Versionable extensible persistence is harder still. Now add the requirement that this state has to be captured in a concise but human-readable way, and it's really hard to do in a way that doesn't introduce numerous footguns. I'm not saying that there isn't some good solution, but I don't know what it is, and I don't think anyone has figured this out yet.
