Actually I think I found out why. In order to get your album artwork and artist/song title displayed for any other music format other than MP3 (.WAV, .OGG) Gracenote is needed. While mp3's store the metadata in the ID3 tag, .WAV and .OGG don't have a uniform way of storing the data always in the same location. In order for Mazda to get rid of gracenote, the would have disable the playback of any sound file other than mp3. Then, people would complain that they don't support more file formats. Gracenote is the only way right now that displays metadata across multiple file formats. Toyota and other manufacturers do this as well. For me, I really don't care about .wav or .ogg since my music library consists of mainly .mp3 and .flac files and I only use .mp3 for my car SSD drive.
Gracenote however is the culprit in slow playlist loading times and often mismatching artist/artwork data. Best solution would be if Mazda would give us an option to disable gracenote via a menu in the MZD Connect system.