The idea of on board speakers for me is to serve as a monitor ... no matter what position I need to be in to serve the room's needs. Sometimes the PA is not in optimal listening range for me, so the KB is my monitor. Since using the Bose ( 2 yrs or so, now )it's less of an issue, but there are still plenty of times that I only use the on board speakers. Nursing homes, cocktail hours, (some small)house parties ...etc
Speakers are a must in my rig. That's why I can't even compare models that do not offer them. They loose at the gate.
Every instrument, every voice, every sound in nature ... these are are all my private tutors ... 24/7 for free, and all I have to do is listen.