Linked suspension is designed to provide a progressive rate.
The link on our bikes are tied to a different point on the frame than our swingarms. This different point causes the linkage travel "Faster" as the swingarm gets more compressed. The closer to bottoming out you get, the faster the link travels upward with the swingarm. This has the effect of a softer feeling at the least compressed point, and a harder feeling at the most compressed point. The benefits of this are numerous and fairly obvious.
While people are playing with multi-spring setup on suspension now, with dual and triple rates, these really aren't a replacement for the truly progressive feel of a link.
I'm guessing the CR500 link is a more modern, better designed setup, and thus why people are moving to it. This is just a guess.
I keep wanting to try dual fox air shocks in a no-link setup. There should be no real disadvantages to this compared to the link setup, and you would easily shave 5-10 pounds off the rear of the motorcycle, and allow for just about infinite adjustability with two air shocks. Even more so if you put both shocks on the same line, and used different lower mount points/different length shocks. It would take a lot of tinkering, but I just don't see the disadvantages to this if you could get the shocks dialed in correctly. The other important part of dual fox shocks is you wont blow your chain off/destroy your case if one of them blew up. The ride would be soggy as hell, but you should be able to easily limp home on one shock.
I'm hoping next winter I can give this a try, with a shock mount point lower/in front of the rail where the stock shock mounts, and a custom chromoly swinger. Now I just need the $2k!