Well the game came out a long time ago, so I am guessing a lot of them could be former players.
It's called the 'Welcome back campaign'. It's a chance for players who already have a FFXIV service account to reactivate it and get a 10 day trial. All of these players have played FFXIV before. The only way they haven't is if they bought the box, setup an account and never bothered to actually log in to the game. The difference between a 'regular' player and one who comes back through this campaign is that the 'regular' player was already subscribed with an active account.
A campaign player simply decided that the game wasn't worth the monthly fee. This would be the majority considering that XIV's subscriber base is less than 10% of the people who purchased the game to begin with. These are the people you really want to come back to the game. If you had a PR disaster like SE had on launch, it would be to your benefit to wow the people who weren't satisfied and left.
Getting those people back probably means just as much or more to a prospective new player as the opinion of someone who stuck it out regardless of how things have gone. There is already a stigma attached to FF MMO gamers that they're masochistic. I'd look sideways at someone who told me that XIV was a great game if they didn't preface it with something to the effect of "I used to hate this game, but that potential that everyone talked about is starting to surface".