system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do toilets tend to be made out of porcelain?
gpt
Porcelain is hard, waterproof, and easily sterilised. It's easy to produce and is glazed to be non-porous meaning it's tough for bacteria to take hold. 

Plastic is not strong enough and it's prohibitively expensive to produce vacuum formed toilets , and stainless steel is cold and not appealing en-mass (from a design perspective). There's no reason to update the design.