You figured it out. Gas mileage is the problem.
Plenty of people want cars that are powerful and fun, yet still economical to drive. That’s why there are a lot of smallish cars in the $25,000-$35,000 range with turbochargers - like the Volkswagen GTI.
Ford is now selling an F-150 with a turbocharged V6 that outperforms their conventional V8 in power, torque, and efficiency.
Even BMW now uses twin-turbo inline sixes and V8’s in their high-end models. Again, efficiency without sacrifice in power is the reason. The lag in these is minimal, I’ve driven them several times.
High-performance naturally-aspirated engines are fast enough these days for any normal person (who needs more than 340 hp in a two-seat sports car?), but given current fuel prices, their poor mileage matters to a lot of people. Turbochargers provide a way to improve efficiency with a minimal ( if any) penalty in performance. Superchargers produce extra power (which is unnecessary), and kill mileage even further. They’re just the wrong side of the spectrum in today’s world.
Don’t forget that, independent of consumer preferences, many companies are also obliged to maintain a certain minimum fuel economy due to government regulation.
Even naturally-aspirated, traditional sports cars (the Nissan 370Z, Porsche Cayman, etc.) are selling poorly - slapping on a supercharger and reducing their mileage even further would be a bad business decision.
Personally, I like the sound and feel of a turbocharged engine. Modern turbo systems have minimal lag - the Saturn Sky could very well just be a turd of a car, which would not surprise me. I really liked the engine in the Volkswagen GTI, which I test-drove just last week. The lag was just enough to remind you the turbo was there, but not enough to be annoying.
For people who must have instant power at the expense of all else, there are plenty of aftermarket tuners who will gladly bolt a supercharger onto pretty much any car you’d like.