I'm wondering if the periodic freeze-the-universe model that many distros use reflects a world that doesn't really exist anymore where distros came on DVDs (or CDs, or floppies). Whatever version you had on the disc, that's the version you're going to use.
I just started playing with FreeBSD in a VM, which has a frozen base system and constantly-updated packages separate from it. This works better for software you don't think of as an "OS component" but the question then becomes where you draw the line.
Or maybe it's just a fundamental disconnect between consumer-facing "move fast and break things" and enterprise-level "never break anything even if it means you can't move at all" and there's no way to make software that works for both.
Which with something relatively small and stable like sudo, is one thing. For big projects on rapid release cycles, like GNOME, it's got a much bigger impact.
Though I do see that Ubuntu does keep updating Firefox and Chromium to the latest versions in LTS, because they're so big and change so fast that backporting fixes has become practically impossible. That looks like a very rare exception to the rule; your typical Python library won't be getting that treatment.
But for Tor, I always use the Tor Project repository. Or for Docker.
And then there's stuff that won't even build in Debian, because it's been developed specifically for Ubuntu.