The simple single piviot design was one of the first rear suspension designs that hit the market, over the years, subsequent designs, more complex and complicated, have been devleoped, but as stated the development of SPV has allowed this simple design to remain viable.
Simple design also = fewer moving parts = less opportunity for failure.
All that positive press on the single piviot, and I bought a NRS, with the multi point Specialized system.
(Screaming deal, as I was saving for my own Heckler)