Here's the secret: the book doesn't make them nearly as much money as a first party VTT/subscription service.
All this content is going to be hyperlinked on D&D Beyond anyway, why spend money to improve it? Hell, making it too accessible might even cost them subscribers.
Oh nice! I'm trying to do the same. Looking for more long form, thought-provoking stuff instead of the fire hose of soundbites and rage bait