Because they are a non-renewable source and is created naturally.
hydroelectric energy is free to the fuel fossil
We find must source better to get energy that hurt wont earth
Oil
fossil fuels can be used as an energy source to power all vehicles and most machinery
Nuclear energy that is the source of sun energy which in turn is the source of fossil and renewable energies.
Chemical energy
No it is its own source of energy
Fossil fuels.
Fossil fuels are exhaustible. Electric energy is an alternative.
Currently, human's conventional source of energy is fossil fuel.
Petroleum is the main source of energy for transportation.