Found this reply in a thread on a three wheeler forum I've been reading. It's a reply about the consent decree that the manufacturers had. He had some good points in his reply. There was a lot more going in at that point in time to help give these things a bad name.
The following is a copy and paste....
It was called a "consent decree". The manufacturers consented to stop manufacturing trikes in order to avoid a lawsuit. Blackmail ? Yes, but the manufacturers had economic incentives. More expensive and therefore more profitable machines (Quads) were sold as a result.
Trikes are harder to master than Quads or Motorcycles. Trikes also had a dangerously seductive association in parents' minds to Tricycles, giving a false appearance of safety to buyers and end users, thereby compounding the inherent danger that much more. The inherent stability in a trike exploits a counter-intuitive predisposition on the operator that consistently causes injuries. Mainly, the instinct to attempt to counter a "high-side" rollover by placing the outside foot down in the path of the rear wheel. That, combined with prevaling attitude of the time which had little regard for safety.
Recently on this site, a member posted pictures of three wheeler enthusiasts from the trike era. Most of these pictures showed individuals jumping and racing trikes without helmets or pads. Others showed children drinking beer at the riding sites, presumably during the rides! Having been a trike enthusiast in the '70's Myself, I can attest to the fact that that was the norm in my social circles!
It makes Me laugh whenever people today try to dispute the rightfulness of the consent decree.