To be fair, SAM and BLM are known as "selfish DPS" because all of their moves are about them. So half of the DPS you've played are designed not to support but to be the focal point of support because man they can do some serious damage.

But you're right, there is a pretty big lack of support in any job, not just DPS. FF14 takes the idea that "damage is the only thing that matters" and runs with it, so outside of debuff cleansing moves like what Bard and the clerics have (and minor things like that) basically all "support" moves are like NIN's trick attack: a move that increases others DPS.