Has everything to do with it.
The OP wrote - hey here is a picture of my bike with and without - which do you like better?
Only thing missing was the poll 
I still stand on my statement that which side of the bike that people take in their photos has nothing to do with whether they like one or two pipes. I'm guessing that it's more a function of the right side being more exposed to take the photo, and I'm positive it it directly related to which side of the bike they happen to be standing on when they snap the photo.

Again, as a personal thing, I haven't taken many photos of my left side, regardless of whether I had pipes on both sides or just one side. But, and again on another personal note, even if I had a center stand, I'd still probably take more photos from the right side, since I find the right side to have a more pleasing appearance. If I am checking out someone else's bike, I will spend most of my time looking over the right side, then I may take a quick walk around to glance at the left side, and unless I happen to see something on that side that stands out as unusual that I like, then I may spend a little more time on that side. I might spend a little extra time on the left side if that bike happened to have a turbo charger, but in that case, I'd be drawn to the other side from what I saw on the right side. If that other bike happened to be on a center stand, then I may actually go to the left side, if I am coming at the bike from that direction, but I'll sure move to the right side shortly. Wow! This has to rank up there with the most ridiculous posts I've ever made...and that really says something.