Getting back to the demise of the Slingshot for practical reasons.
"Still, the biggest hurdle to the success of three-wheelers might simply be most people don't see the point. A three-wheeled car doesn't do anything a four-wheeled car can't do, and it comes at a cost of grip and stability. More tires equal more grip, almost always. And despite their advantages, three-wheelers have many of the same drawbacks of motorcycles and cars. That puts them somewhere in the middle, a novelty. And eventually novelty wears off."
Taken from the article:
Well That Didn't Work: The Ridiculous History of Unstable, Impractical Three-Wheeled Cars