Question

why do you think manufacturers wish to keep their recipes secret​

Answer 1

Answer:

Because sharing those recipes is definitely not going to benefit them and at the present moment they are not legally required to do so. I do not believe that every chemical they use is necessarily toxic but it is likely that some of these chemicals have some environmental impact (anything used in a large enough quantity will have some environment impact).

Explanation:

Answer 2

Answer:

Sometimes because they worked really hard on developing a recipe, and they consider it their signature, and they don't want anyone else making it.