Why is liquified petroleum gas (lpg):?

hello. liquified petroleum gas (lpg) is a form of fuel. Its usage is described by the vehicle it is put into, the same way diesel fuel will not work for a gasoline engine. (I made the mistake of 'trying' that once, it did not work). As a fuel, the 'need' will rise to use its usage....I am disabled, and often ride in a cab, and see that each cab will use its 'new' fuel. Be that electric, lpg, diesel, gasoline. I observe when the cab driver needs to fuel himself up. Now, Gasoline is still the most available fuel.