I like to hear my sound in stereo. When I set up between the left and right speakers, it's almost like I'm in a studio. You get the effects as they were designed to be heard.
Besides, I always have a backup in place. Earlier this year, I had a speaker fail to work and I was so glad I had the other one. I still got paid! No, the audience didn't notice, but I certainly did.
My jobs tend to be 3 to 4 hours, and a lot of the time I can leave my equipment set up from night to night.
If I were doing short one hour nursing homes, I might leave one speaker in the truck.