What happened to Linear Tracking Turntables

After a lengthy discussion with a fellow audiophile who owns a B&O 4004 linear tracking turntable, he wondered what ever happened to the genre. According to him, they do less harm to the groove walls than do current arm geometries. He claims that records he has played hundreds of times sound basically the same as new with minimal wear. My response was--if they were so good, why do so few companies offer them? I'm sure there is a valid reason, but neither one of us is knowledgeable enough in the area to argue the point. Any analog gurus out there who could clarify the reason they fell out of favor.
A decent linear tracking arm is much more expensive to manufacture than a pivoting arm. That's why they disappeared from low cost record players. Linear tracking arms are still around in the high cost category. Another factor is that a well designed linear tracking arm does not require the many delicate adjustments, and periodic readjustments, which audiophiles seem to enjoy doing, so many of them steer clear of linear trackers. No fun!

Some linear tracking arms, using air bearings for example, are overly complex, and have their own share of problems.
My response was--if they were so good, why do so few companies offer them?

Still very much around, but primarily in the high end model turntables. Good examples include Walker, Kuzma Airline, Rockport, Air Tangent, Clear Audio, and Eminent Technology.

Any analog gurus out there who could clarify the reason they fell out of favor.

They didn't fall out of favor, just a lot more expensive to build, and there are many traditional tonearms manufactured today that far exceed your friends B&O.
Just to mention one relatively inexpensive one that I found is the MG-1 by Airtech:


I actually bought it and it replaced my previous Origin Live Silver. The arm is a pretty simple design modelled after the Air Tangent. I'm sure it's not nearly as good as the Air Tangent, but at about 600 including the air pump (I think the pricing is a little more now) the performance was better (to my ear) than the OL-Silver, which I promptly sold. I've no other personal experience with other arms in my system though, so I'm not able to offer any comparison to other arms, alas.
GREAT link Outlier! Thanks for adding that, I did not know about that arm, it looks excellent.
My Revox 795 linear just keeps on trackin'

Was the Bo linear arm a really good idea, I once had one and my dad has one but doesnt that needle sorta "slop" around in the groove trying to find its path? And does that cause damage to recordings that other arms might not, just curious here and it is a un-educated guess.
There is another thread started in the last few days over on the Vinyl Asylum and the variety of linear tracking TTs in use over there is pretty astounding... As I write this, I am listening to a Yamaha PX-1, which sounds great to my relatively untrained-in-top-vinyl-rig ears. Oops... that's the problem with 45s... they're done pretty quick...
Not all air-bearing linear trackers are very complex. The Conductor arm by the Cartridgeman, is an example of an air-bearing with a low pressure pump, thus getting around the problems of high pressure systems.
I really enjoy my LT-30 and Grado Sonata.
After the audiophile community and press clearly and conclusively proved that a

- direct drive with
- linear tracking arms

offered the state of the art in performance...

Some other high margin, garage manufacturer came along proved them to be all wrong, as clearly

- belt drive with
- pivotal arms

was the high end format of choice....

So I would say dont worry, we should see them again soon at your local dealer.
I believe Chadnliz is right, and a LT arm if improperly adjusted can harm a record more and faster than a pivoted arm. And they are hard to adjust correctly unless extremely well-made. So I have always considered LT arms as not to be fooled around with unless very very high end. UHF Magazine's Audiomeca SL5 is a good one.
The Yamaha PX-2 was an excellent turntable, reliable, well made and not astronomically expensive.
The Mitsubishi LT-30 is the best vintage linear table I have ever heard and I had Yamaha PX-2 too. Both modified side by side with the same brand of cartridge. Both are very good especially at the price you can get them compared to the newer TT's. At 33 lbs and dead on you can have kids running in the room and not bother the sound on either. The LT-30 has more body and is more musical in my system than the PX-2 or PX-3 (which I still have too). All the bells and whistles too!