I can understand from an organizational standpoint why it would be attractive to segregate player crunch, DM crunch, and setting lore into different books. But combining the three into one book has proven to be a very successful model. It greatly increases the customer base.
Personally, it doesn't bother me at all and makes the books more enjoyable to read. I'm more annoyed by not having basic monster stats inline in the adventure books.
When I played 1e, I never bought a published setting like Greyhawk, Dragonlance, or Mystara. I don't have any knowledge of lore from Forgotten Realms, Plane Scape, Ravenloft, Dark Sun, etc. so any inconsistencies in 5e don't bother me. I do enjoy the "lore you should know" segments in the Dragontalk podcast and it seems that they at least give a good deal of thought to what lore to use and what to change. In any event, I use a home brew world and just use the parts of official lore that I like and enjoy the rest as an interesting read.
I think many of the new players being drawn to the game by 5th edition appreciate having some "canon" to lean on. It also builds the brand for use in other media.
I've only through the Fiends and Elves sections of MToFs, so far, but I really enjoyed both sections.
Overall, I've been impressed with the quality of 5e material and am glad to see the games growing success. I've had no major disappointments yet.