[Yetiman]

I believe it was due to the single anchor point for two straps, but as of 2006 or so they were no longer SFI approved ans Simpson stopped making them.
I was looking for a set of Simpsons, and they were in short supply at the time. I ended up buying a pair in blue as the supply of black ones had pretty much dried up at that point. I had Simpson lap belts and was looking to add the shoulder straps at that time.