Replying to this 3 days late, so likely this won’t be seen, but I assure you the retention factors are not being ignored. (Well … see my last sentence.). For 2 years in the early nineties I worked in software with an extensive, sophisticated retention model.
Direct pay, benefits, promotion velocity, source of commission were all extensively tracked and modeled. The problem at that point was that you can claim you want a 600 ship navy, but if you don’t have enough surface warfare officers with the right number of years (or dentists or chaplains or JAG lawyers) it’s not going to work.
On the other hand despite our multimillion dollar contract to work on this software, I have no idea if BUPERS actually used it.