If I have missed something obvious in posting this question, feel free to DECIMATE me

This is not an expert answer, but having gathered some info from the past I realized that Roland uses this audio compression routine from the times of the Roland HD Recorders (I cant remember the name of the model now but someone will) and from the time of the very first Groove Sampler SP 808 (if I remember well).

SP 808 uses a ZIP 100 Mb media storage (pretty limited ammount) and here I can see the need for saving megabytes. Though, SP series seem to use the same algorhytm, I think that this id the answer to the question.

The nice thing is that although the audio files get compressed, you can't really hear the difference.

Roland has some crazy-ass algorithm that they use.

That compression probably gives it that certain sound we all like.