What happens to fresh servers on seasonal wipe?

Not sure if many people here have seen the amount of servers that keep opening up, but also might not be aware of the fact that these servers, when put up for the first time, launch in phase 1.

That means that a server posted today, July 25th, 4:00 AM, will have to wait around 6 days just to get to phase 2 while other servers are MILES ahead, with some of the oldest PvP and PvE servers up right now being in phase 3 (server age being 16 days).

So that begs the question, do ALL servers wipe when the time comes? Are people who join into newer servers locked out of the later phases due to the wipe?
Why are these phases on a per server basis anyways?

All in all, it just seems like a strange way of going about things. Even if I were to join a server created RIGHT NOW and the progress doesn't wipe with the seasonal reset, why would I want to be on a server that is now a season behind??