I prefer epoch time for all the reasons you mentioned, but there are situations where you need something else. For example, you can't represent a holiday in epoch time (July 4th has four different start times in the lower 48), and if you need to do precise calculations epoch time is ambiguous around leap seconds.

I wish there was something simpler than 3339/8601, it really is a daunting mess of incompatible implementations and optional elements, but time is hard.