That's because every developer and sysadmin with more than a year of professional experience knows that you never, ever, do your own time zone math. You use your system time utils, and keep them updated so that your code reflects the latest laws.
Though, there are devs that work on those system tools. There are also cases where times need to sync and the changing can cause some issues. Stored times should be UTC but where they aren't it can makes some systems use local time incorrectly for a bit on the rollback. I have also seen network libs in games not use ticks for session starts that would be problematic on rollbacks playing at switchover. There have also been flaws in system time utils previously.
Lots of unnecessary potential edge cases, all for an unnecessary time change of time itself except a few places like Arizona.