Funny, we've just seen the 'elitist' meme in the bluegrass and classical disciplines, maybe it was inevitable that the spotlight turns to jazzers. I said my piece on that
here. But I'd like to address the question of why workshops tend to focus on jazz, speaking as an R&B guy who can get by in the jazz context.
If you're taking a workshop, I'll presume that you want to learn more about music and how to handle your instrument. To me that means deeper understanding of harmony, rhythm and melodic structures, technique and tonal control, yes, but most important is learning how reach inside, find your own music and express it. Jazz is where all those aspects come together.
Jazz has always been about starting with the familiar and actively seeking ways to go deeper and express wider. What you learn in that realm informs and expands your knowledge and facility with any kind of music. You don't have to have a special affinity for the song "All of Me" to appreciate what a master musician can do with it, and that's the real lesson.
Musicality, technical skill and harmonic complexity may have generally fallen out of favor in popular music since the '80s, when nihilistic punkers decided that knowing anything was elitist and the rappers tossed melody out the window in favor of mechanical contrivance and dance moves, but for musicians those choices are self-limiting.