That's a little oversimplified. I agree that's the function of binders, but isn't it also essential for the skier to trust that his boots will stay attached to skis with said binders? A binding that doesn't do that isn't a very good one (although it still may hold the boot to the ski).
I'm sort of playing devil's advocate, but if a skier doesn't trust their gear, then it will be very tough for them to ski as hard as they may want to.
I mentioned in an earlier post why I don't purchase Marker (CN: had 2 pairs blow up on my when I was younger). But that's me personally. I've only skied the Dukes out of the Jester/Griffon/Baron/etc. lineup, and they were adequate but not my favourite. I don't hate them and I might recommend them to someone, but I wouldn't buy them for myself. The Jesters seem like an average-to-above average binder, but I have no experience with them so I don't have an opinion. If they work for someone, then awesome!