Yes I also vote on contribution, but I think if I'm powering up and keeping most of my Hive powered up I just apply the same standards to others!
Some of these witnesses have sold off hundreds of thousands of dollars worth of Steem and Hive over the years. I kind of expect more of a long term view from them!
RE: Why do 5 of the Top 20 Witnesses have less Hive Power than Me?