For me, it was ease of set up. The Hennessy lashing--per side--took me a minimum of thirty seconds (usually closer to forty-five) to tie. About the same to untie. I'd have to do that a minimum of two or three times when I initially set up.
With descender rings or whoopies, it takes me approximately thirty seconds to set up each side...but, it takes me approximately two seconds per side to adjust. That's a savings of about five minutes on set up. I like things to be easy when I get to camp; I'm usually pretty tired after a long day on the trail or road.
Also, the descenders and whoopies are a lot easier to do when my fingers are cold (which, admittedly, isn't as much of a concern down here in FL).
So, that's why I switched. Not because the stock suspension is bad, or faulty, but because the other options out there are easier. That's all.