I don't know what a person does who cannot do dairy or soy. If it is not one, it is the other. Fortunately, both are on the list of allergens that have to be called out explicitly on food labels.
My lunch plans did not work out and I really needed something so I grabbed a gluten-free dairy-free Amy's Shepherds Pie out of the freezer but it does contain soy. I confess I ate it anyway. So far I have not managed a soy-free day yet. Oh well!
I am so thankful that the 8 most common allergens are actually listed clearly on packaging. My son is allergic to some of those, as well as sesame seeds (and other seeds.) I have heard sesame seeds are the 9th most common allergen. I am bummed seeds are not called out like the other things he is allergic to, as that does make things easier. And we all know how hard it is to figure out if something contains gluten or not!!
My point is : Even though soy is everywhere at least it is listed clearly.