The reason is because the FAA feels there isn't any significant improvement in the tasks that a pilot needs to perform these days by having the ability to rebuild the airplane by scratch.

I have always been pragmatic in this sense. If I cant touch it, interact with it or fix it from the cockpit, there is little reason for me to know how it works above the rudimentary information. I mean, knowing how many bolts hold engine together is wasted information that I could better use elsewhere.

They should get away from system heavy knowledge and focus more on real world scenario training as that does far more to enlighten modern pilots that knowing the gearbox crap.

Anyway, thats my take. I only have so much room in training to absorb stuff, prioritize it with stuff that I actually need to know.