why BIAB when you can use an arranger KB to easily record backing tracks that sound amazing..?
A few reasons, Donny.
1. It's very easy to make changes and/or edits without having to rerecord the whole thing (one of my pet peeves about my PSR).
2. Price. The everything pack is much cheaper than a new arranger.
3. With the realtracks technology it is very easy to regenerate a track you don't quite like the sound of, again without having to rerecord the whole thing.
4. Realism. I haven't heard a style from any arranger that can come close to the realism level that BiaB can do. In this particular song the banjo immediately comes to mind, as does the mandolin. These are tracks of actual players playing real instruments; not a MIDI simulation. BiaB is also able to generate more interesting parts because it knows in advance what the chords are. The bass lines can walk up to the next chord change instead of just playing the same repetitive pattern over and over and over, as an example.