If plastic comes from oil and gas, which come originally from plants, why isn’t it biodegradable?

Plastic is made from oil and natural gas, which started out as fossilized plant and animal material. But buried deep underground for millions of years, those materials changed in important ways.

Source: If plastic comes from oil and gas, which come originally from plants, why isn’t it biodegradable?

Is Plastic Recycling A Lie? Oil Companies Touted Recycling To Sell More Plastic : NPR

An NPR and PBS Frontline investigation reveals how the oil and gas industry used the promise of recycling to sell more plastic, even when they knew it would never work on a large scale.
also: https://www.marxist.com/capitalism-s-recycling-lie.htm

Source: Is Plastic Recycling A Lie? Oil Companies Touted Recycling To Sell More Plastic : NPR