The First and Second Law of Thermodynamics say that when converting one form of energy to another, there will always be losses. Converting chemical energy (burning any kind of fuel) to mechanical energy has a lot of lost energy (put your hand next to any running engine ... that is heat energy you are feeling).
We have used these lossey devices ("engines") for hundreds of years because the fuel was cheap and plentiful. Relative speaking, these fuels still are.
Electric to mechanical energy (a motor) is actually pretty efficient compared to an "engine".
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