Social activity in mmorpg's generally work off of how the game is developed, how you develop a game and it's environment will effect how the player interacts within that world. It seems SE decided to go with lower social interaction to get high accessibility, while it can turn out high sub numbers the amount of sustained gameplay is lower which is why you hear suggestions from Yoshi-P to take breaks between content. Duty Finder allows a person to easily jump into content even from a low populated server relatively easily, it comes at a cost of server options looking subpar. Easy and cheap teleportation, lack of server side content, easy FC creation, massive solo-able content, meaningless non-instanced areas (which are server confined), etc. All of those make it easier for a solo experience made bite sized which doesn't encourage social interaction.
While you may not be suggesting this but I don't think people who see less interaction in FFXIV are more anti-social, it's one of the first things I've noticed while starting this game and I don't consider myself anti-social (as I've played many, many other mmorpg's and had no problems socializing with various guilds/groups). While a great game in almost every other respect, FFXIV does have it's problems encouraging and (more importantly) maintaining social activity, which is one of the main features of a mmorpg which I don't think can be contributed merely to the modern age.