It is also usable for those players whose only (or at least first) job to level60 is one of the advanced jobs (DRK, AST and MCH). Those players earlier were not able to level their retainer past 50 in whatever class they had worked with until HW. I don't think the retainers being able to have jobs was never meant to be improvement as such. It was just added so people with this particular case would be on equal grounds as there was some complaints after HW launches, and the ability to wear job based Relic equipment is already a bonus.