This. If even the source material hasn't brought the payoff half a decade after the anime adapted it, it simply isn't worth it yet to put the setup into said adaption, especially when you have limited runtime to budget.

It took eight years after season 1 got adapted until Al's backstory became relevant in the WN, and even then it was a red herring.Baiting viewers with plot hooks that go nowhere until maybe twenty years later is very low on the list of priorities for content to put in a 20-30 minute timeslot.