Why would my name plates not show titles....

Its only showing the name and health.

Mostly I'd like to see the type of Vendor or Trainer npcs are in the city without mousing over every single one.

When I get closer to an NPC its nameplate changes from "Name - Title/Job" to "Name - Health Bar"

The Blizzard settings are set to show name / title but its going away for some reason, anyone know why?

That is the intended behavior. You can try using the addon Aloft if you need more information in the nameplates just be aware that Aloft has an impact on performance since it treats every nameplate as a unitframe.