The reason I have mine on the right goes back to how I arranged my Desktop before OS X.
In those days, the hard drive icon sat in the upper right corner. Below that, I had a single column of icons that consisted of aliases to my most frequently used applications and my most frequently used folders and files. That stretched all the way down to the bottom right corner, where the Trash sat. I can’t remember for sure, but knowing how meticulous I can be about such trivial things, I’m guessing I curated that column of icons to keep it from spilling over to the left to a second column.
With the Dock on the right, always set to its largest size, and with my Finder preferences set so that new windows open to the Home folder, I was able to largely re-create the arrangement I had grown accustomed to in ye olden tymes.
A secondary reason is that I like my windows to be as tall as possible, while I rarely run out of horizontal space. For me, there is almost always more than enough horizontal space and almost never enough vertical space.
I’d love to use auto hide, but when I slide over to make the Dock reappear, the delay is always just long enough to annoy me.