I'd like to add an opinion.
I use an arranger out of necessity and laziness. I used to play multiple keyboards and bass pedals in a trio. We kicked butt. changes came along and then it was me and the drummer, two pieces and we still kicked butt. Drummer leaves for Florida, tried some new ones, none could fit in like he did so I went to a drum machine. Used it for a long time along with two keyboards and pedals. Got interested in arrangers and said "why am I working so hard dragging all this stuff around and no one cares. Began using an arranger and bit the bullet and started DJ-ing along with it. Sorry but I just couldn't hack trying to do the "Electric Slide" live.
So here I am ,still trying to push the live keyboard/vocals but the DJ thing is what they want. When I do do the live thing I get great response but then its on to the next party. Recently did a Bridal Shower brunch and they loved the live thing. Got booked for the Wedding cocktail hour, My favorite is doing a cocktail hour on a good piano, people love it because its new to most of them. If I could I would go backwards and do the keyboard/vocal/bass pedal thing again. It was the most fun. But bottom line its the public that dictated the business. Many many acts I see today are just Kareoke backrounds and live vocals and it sells. So arranger and backround MP3 players will continue to sell
to those who want to have fun on their own or try to sell live music without a band.
Just my $.02