devtrackers.gg
Doesn't really have anything to do with it. It's more about server infrastructure and each game's technical design.
Downtime isn't a thing for GW1/GW2 because, to the extent that they have or have had in-game "worlds," they are distinct from the underlying server architecture, while an FFXIV data center or world is tied to specific hardware and characters are tied to those worlds.
With GW1/GW2, they're able to simultaneously host instances with different builds of the game. This means that ANet can put out a patch, spin up instances for that new patch that players will enter as they log into the game with the new patch, and players can keep playing on the old build while that's going on. This is why you'll get a message saying something like, "New Build Available. Log out within 2 hours." They don't want to host the old build indefinitely, but they don't need to interrupt your current session or kick you out of the game for hours at a time.
