The appeal of the three-wheeled car is very simple. Emissions controls and safety standards meant that cars of that era got shitty gas mileage, had poor performance, and cost a lot of money to build and buy. A three-wheeled car would sell like hotcakes in the recession era of 1980!
As you can see, transitional economic conditions often result the development of oddball cars. The problem is, of course, that recessions end. People make more money and they no longer want poverty-cars. In the 1970's, maybe such a "car" would have sold, in limited numbers. And yes, people tried back then to build three-wheeled cars - it turned out to be a scam. But by the mid 1980's, when the economy started to recover, sales would taper off to nothing. In a way, it is like the recession of 1958, which spawned the Chevy II, the Falcon, and the Valiant (and put VW on the map in the USA). Small, cheap cars started to sell well in America, then, but by the mid-1960's, everyone wanted a big-block "Muscle Car". When the oil crises hit in 1973, we got the Vega and the Pinto. The car business is cyclical this way. Remember how many Honda Fits were sold in 2009 - and how many monster SUVs have been sold since then?
By the way, if you want to see a collection of three-wheeled cars and microcars, check out the Lane Museum in Nashville, Tennessee (yet another good reason to go there!). Sadly, the Bruce Weiner Microcar Museum here in Georgia closed a few years ago and the collection was auctioned off. You can still "virtually" visit that museum online, though. As you can see, the idea of a simple basic mico-car or a three-wheeled car is one that has been popular many, many times in the past, usually in response to harsh economic conditions. And in nearly all instances, such poverty-mobiles had a brief heyday in the sun, or were utter failures in the marketplace. They never really took off for the long haul.
More puzzling still, the vaunted Elio car is said to be equipped (in theory, anyway, none have been built, other than rough prototypes) with airbags, pollution controls, etc., negating the cost advantages of the three-wheeler. If you equip such a car with all of that stuff, you might as well cut to the chase and add the fourth wheel and just make a regular car. Airbags aren't cheap, and neither are emissions controls.
Will we see three-wheeled cars in our future? Probably not. The Elio seems to be slowly fading from view, as each date for production or other goals comes and goes with no activity in their used Hummer plant happening (other than, apparently, selling off the machinery!). And economic conditions worldwide are getting better, overall, not worse, even if it seems that a recession is on the horizon. Even in India (especially in India), Tata motors is trying to wean the public of the "tuk-tuk" type three wheelers in favor of their new four-wheel nano car. When people have a choice and they can afford to do so, they favor a more traditional four-wheeled car. Three-wheeled cars are usually not a choice but something people are forced into buying.
Sadly, like with the Tucker, or the Bricklin, or whatever, there are always a few rabid "true believers" who are willing to suspend disbelief to put a religious-like fervor into a vehicle or other product, for no apparent valid reason. And often these sort of folks lose their shirts as a result. Never make a consumer good into a religion or believe it will change the world. Don't invest - or put down payments on - wild-eyed dreams. Sadly, the people who are losing money on these sorts of deals are people who can least afford to lose what little money they have. But then again, they have no one but themselves to blame for being so blind to the obvious.
I realized, even back in 1980, that the three-wheeled car was little more than a marijuana-fueled fantasy. It made a lot of sense after a number of bong-hits, but then you sober up and realize that it really makes no sense, economically or environmentally or from a safety standard. And maybe right there is a good reason to give up on pot and pot-fueled fantasies.