everything is a trade-off

Well, I'd say you've been lucky so far. I often face tiny breakage upon upgrade. It's always tiny stuff that scripts were relying on, such as a script that was checking for the battery state in /proc/acpi, iptables modules being reorganized and renamed, a network driver change which does not react similarly to tuning settings, a deprecated mount option that's no longer supported by a filesystem, etc. This is never too serious and often easily fixable once you understand what's happening. The thing is, users engage into LTS distros to benefit from fixes *without* having to deal with such trouble, and that's the deal. When users don't care about this, they just don't use LTS distros.

And there's of course the long list of possible regressions that come from feature improvements which you are not necessarily interested in but cause harm. When they render your system unbootable and hard too fix, the next time you'll simply skip the upgrade. This is not specific to the kernel but common to all software. There are branches which only receive fixes and that come with a much lower risk of regressions than branches getting new features and architectural changes, and users who validated a version don't want to break everything when just trying to apply a security fix.