Mr nrose101,
While it is true that the mp4/m4a was not created by Apple, it is directly based off of an Apple technology called QuickTime. Even the oft wrong or misinformed Wikipedia will tell you that.
Also, I agree that the mp4/m4a is TECHNICALLY a better audio format. However, scientifically speaking, it has been proven that MOST people cannot hear the difference between a mp4/m4a or a mp3. Encoding has also come a LONG WAY on mp3's in an effort to increase audio quality.
The problem I have with the mp4/m4a is that it is not as universal as the mp3. Most Microsoft based computers CANNOT play an encrypted or unencrypted mp4/m4a file without some form of 3rd party software (iTunes, VLC, etc) or downloading an audio codec to add to Windows Media Player. Since over 80% OF THE WORLD use a Microsoft based computer, it would seem foolish to use a format that require a person to have to download something else just to listen to it...but people do.
My car stereo even has a USB port that I can plug my iPod into or a USB Flash Drive. The Flash drive is a neat feature since I can dump a bunch of mixes onto the flash drive, take them out to the car, and listen to them in a REAL WORLD environment. Guess what, the USB port / Flash Drive thingy only works with MP3's.
FYI, I am in the Recording Industry, we make music ALL DAY LONG so I know a thing or two about music. When we send out music, we ALWAYS use the MP3 format because it is UNIVERSAL.
Enough research for you?