So this line of thought got kicked off actually a few weeks ago, when I saw this blurb, from the letter from the producer for Final Fantasy XIV - ARR, in response to the question What can they do about the continued lack of tanks in the game?
We review player data every day, and recently there are actually a significant number of players leveling tank classes. When participating in the low level duty roulette, for example, you'll encounter players leveling their tanks and even players that just started a tank class. The number of tanks around level 40 is growing as well, and I believe this number will continue to increase. However, as you all know, there are also a number of players who are simply leveling a tank class because it's easier to queue in the duty finder, so whether or not these players will continue to play as tanks in the long term is still an issue. As things stand now, however, the number of tanks is growing, and I'm sure there are many players who will find tanking to be fun and continue leveling them up, so we're going to keep an eye on how many decide to use their tanks as their main class. If tanks are still in short supply, we would like to consider adding various bonuses such as a specialized mount.
And quite honestly this just flumoxed me. The need for tanks is so great in Final Fantasy that the producers of the game are considering bribing people to roll up tanks with specialized mounts. And Final Fantasy XIV certainly isn't alone in this. WoW has stuck with a strong role combat model (that is, a model that incorporates the oft referred to trinity of tank, dps, and heals) for over a decade, and it still struggles with a lack of tanks in random group play. And if it's not tanks, then it's healers. And it struck me - we've been doing this for over 20 years. Why isn't this a solved problem yet?