Yes, if you are creating appointments in a calendar program and want to have a daily meeting at 3pm and you are in a jurisdiction with DST, then you will need some TZ info so it knows when to wiggle the time by an hour.

But in this case, there's a lot of other information you want to store: first date in the series, repetition frequency, time of the appointment, location (e.g. "Europe/London" as opposed to "GMT" or "UTC+0" which would not be adequate). Basically, you're not so much storing a series of dates as storing a thunk for generating dates.