Many people power down for many reasons and it's completely understandable. In the US you owe 35-45% in taxes which requires a constant power down. Many witnesses are paying as much or more than they make in witness rewards, potentially requiring a constant power down.
There is heaps of difference between Steemit Inc powering down and hiding their stake and a standard user powering down, witness or not.
I won't deny many witnesses powered down most or all of their stake, and while I don't agree with it, that is their right.
I fully agree, its within everyones right to do what they like with their power, including steemit inc