Please add holidays events in later cities

[Seraphor]

You answered yourself already. It is because new players. Even Ishgard, which is the first one outside base game, still require a lot of hours to reach. At level 15-30 players can still enjoy events without having to rush the game.

A solution would be to double up on the event locations. So you can either start the Starlight Celebration in Gridania, or in Ishgard, and once you've completed it in one, you've completed it for both (but can do the repeatables in either).
This would not only be more lore friendly, and provide an avenue for new plots (the new Ishgard Starlight event could be a new plot while the Gridanian version could be a repeat of last years or of... 2018 or something), but it would also ease up on congestion lag, spreading players between two zones instead of all crowding into one.