Op you are probably one of a very small minority of those that never go back to a zone once they've gone through the MSQ. Though I'm sure you generalized it as I know you would have (unless they changed them) gone back to other zones in order to complete Shadowbringers msq as you'd of needed to finish one of the role quests. Which I'm sure would have you visiting zones after the story has finished with them. The reason a lot of others go back to these zones are all that Jeeqbit stated. Heck starting in Shadowbringers one of the two world boss fates requires flight to even participate in them. Then there are the seasonal events or many of the cross over events with other games. The Yokai even asks you to grind fates from ARR, HW and Stormblood zones and you will not make it to as many fates let alone get enough credit for them without flying.