Correct me if i'm wrong but i was under the impression homebrew emulator developers have bigger barriers to overcome. Nintendo has full time developers working as their day job and also is the owner of the system so they should know about it's inner workings, quirks, etc. Homebrew developers work solo most of the time with some help, if any, they have to do this in their free time, sometimes real life forces them to abandon their projects for years, etc, and they also have to figure out how a system works by themselves.
Sure, it takes a long time for a good emulator to be created but a company like Nintendo does have a good head start. Also, aren't they emulating their systems since the Wii anyway? They should already have a 10 year experience with this stuff.