Why would it be outlawed? Too expensive, or does it just work too well and doesn't lend itself to promoting the crashes that the spectators love to see at motor vehicle races? 
I hate it when arbitrary rules stifle technical advancements for no apparent reason. (I was one of the few people that seemed to like the idea race cars powered by gas-turbine engines.
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A combination of trying to keep expense in check, and there was this thought that the bikes were becoming too "auto-magical" and that it would make the rider less important. I remember an excellent article on this back over a decade ago, but I cant remember where I read it. It might not have even been online.
The funny thing about the magnetic shocks that you see on Ferrari, Lamborghini, Mustangs, and of course Corvettes... its that it was made by Chevrolet and every high end car with it pays a license to GM to use the tech... GM is also the one who figured out how to mass produce carbon rotors on a large scale... so same deal there.
Ford has a pretty slick cheap shock valve coming out now... it can "lock" the shock when it detects a pothole, so the wheel doesnt drop in and you dont hit the otherside as hard.
You can read that one here:
http://jalopnik.com/the-2017-ford-fusion-v6-will-hover-over-potholes-1760056085being an electronics nerd, and a motorsports nerd means I spent a lot of time reading about electronic suspension control. I wish I had more hands on experience with the stuff, but most of my knowledge is just from reading about it... Ive driven a couple magnetic ride vettes, but not on a track.