In their day, steam cars offered power and familiarity. In the early years of motoring, steam-powered cars were among the fastest around and a lot of people knew how steam engines worked.
Their one big drawback was that you couldn't just get in and drive them. It took a long time to heat up all that water. The invention of the electric starter for gasoline cars, which did away with the need for difficult and dangerous hand cranking, finally sealed the steam car's fate.