Waste incineration to create electricity, and also (according to those companies) to reduce emissions from landfills, and the need for land for waste.

Even if you think it's going to landfill, a lot is not.

And when it's burned, plastics are released into the environment, if not immediately then over shorter time than if they were left intact and buried.

It's best in every single possible way, except for one: Emotional people who don't realize it's the best way.