NYPL has mobi books that work on a Kindle with no DRM stripping required, but I guess it's still not strictly 'native' and not supported by the library.
You need to put your Kindle's pid on your library account, and non-techies can get their Kindle pid at web sites like:
http://kindletools.prestonlee.com/
Yes, ADE epubs are dominant, but to say "Kindle can't" is just wrong, which was the probably motivator behind the big colorful font.
ApK