Why does every piece of lore have to be thirty pages long now? What happened to simplicity? Why does everything need a scientific explanation instead of "a wizard did it" in a fantasy world?
Lago, some of the earliest lore, such as the creation lore, was much simpler than newer lore. Back then, a wizard did it was used, now everything has a dumb convoluted scientific explanation that takes 3 pages.
Was actually "an aengul did it" but I get your point. However, this is neither a new nor ubiquitous thing. Some people write tons of stuff, and some are concise. That's their choice. It isn't necessary and doesn't improve chances of implementation.
They do it because a long explanation is more likely to be accepted than a short one, because humans like overcomplicated things, because they seem more serious, more "official".