Hello!
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It's not a matter of Jerry not WANTING to do it. It's more like it CAN'T be done, even if he DID want to. Even being able to upgrade WITHIN a point series was a major accomplishment in itself for LL. Very few other distros, if any, can upgrade as seamlessly as LL can within a series.
Let's try upgrading from Ubuntu 15.04 to 15.10, as an example. Chances are, it'll work, but it's also roughly 50-50 odds that trying to upgrade will also totally trash your setup. Even Windows recommends a new install, as opposed to trying to upgrade what you have - let's say, 7 to 8.
The reason it is NOT possible to upgrade across point versions is because so many changes would be required, it's just plain easier to upgrade to the 3.X series as a new install. It's like trying to make minor changes in a car's trim to make one year's model into the next year's model, when that model was completely redesigned from the ground up...
73 DE N4RPS
Rob