Oh, I know it's easy to fix, I just single that bug out as "I have done nothing with this box but install updates and surf the web. I am Grandma. It breaks".

If you're Grandma you don't have /boot on a separate partition, you have all / on a big 120GB at least, so if you run out of space you simply know you've run out of space.

Not perfect but not a problem for 90% of people I guess...

Ubuntu installer has separate /boot partition by default. If you don't do anything special during installation you end up with it.

No you don't. Ubuntu's default partition map is one big / and one efi(if necessary).

I literally just did a BIOS install and it has a separate /boot.

I assume it changed recently, I've seen fresh 2014 installs with tiny 255MB boot partitions.

This was ubuntu's recommended/default partition plan. I did not customize it. Now, it's possible this is a plan they no longer recommend and have changed since I first installed Ubuntu, but the point stands:

I installed Ubuntu onto a machine, chose the recommended default options, and it set up a /boot partition that was quite small, and its normal update cycle fills it up and fails to fix the problem automatically or prompt the user with information to fix the problem.