When I tried a couple "plastic" enclosures they too were made of HDPE "food safe" material. Various reasons why I didn't care for them, but for me, snakes health is #1.
I'm not going to get into a debate here on this, BUT...just remember that none of those other uses you mention involve heating of those containers, much less CONSTANT heating of them in use. Just saying...it matters. Even frozen foods intended to be cooked in microwave say right ON them not to re-heat in those containers...why? Because heat breaks down plastics. (Cold is just fine, but last I checked, our snakes need heat.)Also, we humans are MUCH bigger than our snakes...and our bodies are more complex too, likely way more resilient when it comes to chemical contaminants, don't you think?