I agree with most of the above.
But the difference, or excuse in my case, is that I am not close to as fit or as fast or as light weight as a pro, so very little of their setup applies to me. Although I do agree with the theory in an ideal world.
My riding style isn't correct, I get tired quickly and my suspension setup isn't perfect either. So a little bar raiser isn't going to cock it up for me.
As I said, do what works for you.

But my riding efficiency improved manyfold once I moved from the perceived comfort of the bar risers (they absolutely are much more comfortable for easy peasy merkating, when I believe it is not even necessary and sitting would be much better) to the efficiency of the 'correct' set-up in the technical riding. As an example, few years ago I used to ride KTM300 with risers in DeWildt almost every weekend. I was younger and fitter, and as far as I can remember I was never able to ride it from shabeen back to Police station in one go. Yesterday I did it on KMT 500 from shabeen through Police station all the way to Midrand in one go (which included about 25 km of tar admitedly). And I feel much more in control on the bike - for example on those 15 km or so of whoops you do on that track - weirdly enough, the lower I have my chin to the bar, the better - smoother and faster - I'm able to ride them, as my hands work much more efficiently at damping them. It really was an eye opener for me.
It really is so much more efficient to get the technique right (and bar risers in my experience detract from that) - those Pros are not using it because it is fancy, but because it works.
If you are up for a little experiment, maybe take the risers off and go for a ride to DeWildt (I would recommend at least three rides - it will take some getting used to) and see what happens (you ride 500, right?) If it doesn't work, just put them back and you are done, but I suspect you might be pleasantly surprised. And don't be afraid to crouch ridiculously low - just try to keep your chin above the bars not too far back.
I'm an average bimbo at best - getting my 45 year old ass kicked by 55 year old weekend warriors regularly in DeWildt.
Again, just my 2c - not criticizing one way or another, but this simple thing improved my riding so much that I think it is good to talk about it here.