It’s because you can’t recycle plastic really. Each time you heat it up to melt it it loses its properties. A recyclable material is for instance aluminium, which keeps on being awesome. I tried various recycled plastics for a business I run, none of it was strong enough. Recycled lego, recycled car bumpers, nada. And then the question is - why would I buy the recycled plastic that doesn’t work when it’s like 30 cents cheaper. Pellets are so cheap in fact, that I could buy a tonne, use up 100kgs, throw the rest away and still be fine.