In the early days of cars, you could buy several different types of engine depending on your preference. For example, there were the Stanley Steamer, other steam powered cars as well as electric powered cars on the market about 100 years ago. In the end, the gasoline powered internal combustion engine won out in the marketplace.

Over the years, several inventors have tried to make cars that were not powered by internal combustion engines. For example, Bill Lear spent millions back in the 1970s trying to reinvent the steam powered car. He failed to make an engine that got better mileage than an internal combustion engine although it did run very well. The problem is that steam engines have lower thermal efficiency than internal combustion engines.

Several attempts have been made to build electric cars but all are limited by the low energy density of chemical batteries. Hybrid-electric cars are much better but they still depend on an internal combustion engine. There's also the factor of added cost for a relatively modest increase in mileage according to this Forbes article.

Odds are the best bet over the next 10-20 years will be fuel cell powered cars. Right now, fuel cells are way too expensive (around a $1000 a kilowatt according to some sources) for that use but companies like Ballard are making great progress with the technology. Until the cost can be made affordable, it won't be successful in the market. It's no conspiracy, just hard engineering and economic facts confronting a proven technology that keeps getting better.

You also have to put the technology in a vehicle that people are willing to buy. If you want really good gas mileage, you can already buy cars like the Suzuki Swift. Not many people are buying them, through. According to that Forbes article, of the 17.2 million vehicles sold in the US last year, only 2,547 of them were Swifts and less than 20,000 were hybrid-electric cars.