Why are coal and petroleum considered non renewable sources of energy?

Coal, oil, and natural gas are formed from dead animals and plants over millions of years. As the world's reserves are burnt, there is no new source to compensate, so eventually all will be consumed. Until the advent of fracking, it was assumed the Earth had 20-50 years of oil reserves left. Peak coal is expected near 2025. Natural gas is expected to peak near 2050.