Only a few people have to maintain the time zone system, and only a few people (those writing the software that everybody else uses) have to understand the minutiae. The alternative is that everybody has to understand, which will invariably cause many mistakes.

I mean, when someone schedules an across-timezones meeting they use software anyway; and who really cares about that one time 2 decades ago when some small region switched timezones or whatever? (yes, I'm painfully aware that there are changes to timezones across the world pretty much every month; what I'm saying is how often does anyone really care about the historical changes, in contexts where the hour or 30 minutes really matters?)