Keeping things simple imagine 10 people play the game and each pay $1 each for the service. After a while one player decides the game no longer holds interest for them, SE now makes $9 a month rather than $10. SE certainly would rather make $10 a month and so they do what they can to appeal to the widest base in order to keep and attract customers back to the game. They try new things (some of which doesn't work, some which does), they advertise, they do call backs, invite a friend.

Now under the new system 10 people play the game, 9 play for "free", and one pays $10 a month. Now if SE loses a customer who is playing for free it's not a big deal, but if they lose the paying customer they are in trouble. Now to ensure they earn money they need to keep appealing to the narrow paying player base. Free customers (or even the larger portion of customers who willing pay their $1) no longer matter because the bulk of their profit is tied up in the few players that are paying $10 a month. Rather than trying to give the player base new and different thing they hammer on the few things they know keep the whales paying.

This idea of appealing only to a very narrow portion of players carries a huge risk, if the free and "almost" free players leave the game because they feel like the devs have abandoned them, the whales too will eventually leave. However if they don't appeal to the whales and the whales do leave, SE loses income. Think of this like the high risk high reward. Games setup this way can make huge profit, but they also tend not to have much longevity.

How then can WoW get away with this? Well WoW is an anomaly among MMOs. I could have an hour long discussion as to why but to keep this as short as possible, WoW was in the right place at the right time and played their cards exactly right. FFXIV while successful cannot compete with WoW in anyway and SE should not necessary take it as a given that some financial model that has done well for WoW will work for FFXIV.

Think of FFXIV vs WoW like this - under the proposed model, FFXIV has 9 free players and 1 paying. WoW has 90 free players and 10 paying. (This is exactly the same proportion of paying to free players.) FFXIV loses 1 paying customer it's lights out but if WoW loses one paying customer it hurts but there are 9 others with time to attract more. The smaller population alone in FFXIV makes this a huge commercial risk, and given how they have been handling marketing, and statements from SE along the lines of "well you can take a break if you want", suggest that SE are comfortable with the idea that they have players who will pay a sub for a few months around a story release and then unsub while waiting for new content. Combine this with regular call back campaigns and the high volume of advertising around expansions SE gains very little by "keeping" free players through a token system.