It's because most of them are focused on heating in microwaves stove tops ect. As long as it's BPA free (which all should be) you'll be safe.

I had the same concern, There is a couple on Amazon just search stainless steel dehydrator

I was looking at this one, but went with the 9 try Excalibur. Love it

Dehyber Food Dehydrator(67 Free Recipes) ,8 Layers Stainless Steel Jerky Fruit Dehydrator with Adjustable Timer and Temperature Control,110V 600w Food Dryer for Fruit,Beef,Jerky,Dog Treats,Herbs https://www.amazon.com/dp/B096YCNXFQ/ref=cm_sw_r_apan_glt_i_W4V6JWP429KWXP4YWV5N?_encoding=UTF8&psc=1