Do you know why we don't turn waste plastic into lumber?

Something like:

https://materialdistrict.com/article/building-blocks-made-re...

or

https://inhabitat.com/lego-like-building-blocks-of-recycled-...

Hi OP here, I've been asking everyone, professors, VCs, founders, chemists - and can't get an answer. The solution seems to be so simple, if you have millions of tons of plastic waste, let's turn them into millions of tons of other things, like pavers, sidewalks, and plastic lumber. I'd love to hear what HN thinks about this. Thanks!