Well, mainly for our cats’ water fountain.
The main reason why I bought it is that whenever I clean my cats’ fountain, I find that it is virtually impossible to make sure no more detergent residue stays in the fountains’ parts, and sometimes I find myself having to rinse more than once over to remove the soapy water. To make sure that I don’t poison my cats if there really is any residue left over, I got us a baby accessories detergent that is made of food grade ingredients.
At least now when I wash their stuff, I don’t worry that the soapy residues might turn them off drinking water, or that they get poisoned or get diarrhoea.
Not cheap though, but I reckon it is cheaper than pet bowl cleansers.