Maybe because we use
it mostly as a stabilizer in the food industry, and we think that, as most of the stabilizer, it's there only to enhance the final product, and it is not an essential food.
Among the best cited: real trees are
mostly grown in North America, while the fake ones largely are shipped from China; and, the vinyl often used in fake trees commonly includes a great deal of inorganic lead
as a «
stabilizer» and / or fire proofing agent, requiring a Prop 65 warning label in California.