Because the soy industry pushed the ingredient. I know first hand the deceit they used to other food industry companies. Remember my BIL was one of the 22 fired for saying it was not a good ingredient and should NOT be used.
Observant Jews still eat sushi and sashimi in NY during Passover (sashimi has no rice, sushi is raw fish placed on blocks of rice). Obviously they can't put regular soy sauce on there so they use FAKE SOY SAUCE like LaChoy.
According to the company's own history on the net this product was developed so that Jewish people in San Francisco and Japan and Hongkong and Singapore could eat Sushi during Passover..
Which sounds quite reasonable all things considered.
Anyway it really doesn't taste the same but it's better than nothing and used in small quantities LaChoy and several other brands of fake soy sauce do the flavor job they are supposed to do with sushi.
We eat lots of sushi so this is a real issue around here.
You can "test" your allergy focus with this fake soy. There's no wheat or barley in it, so if it doesn't bother you it's the wheat or barley. if it does bother you it's the soy, but it's not the product of fermentation. That's a whole different problem and I don't know the chemistry well enough to understand it all.