Various Sugars in wet cat food

Hi all,
I have been looking into feline nutrition and watched a few videos saying that cereals are to be avoided in the nutrition of these obligate carnivores. I then took to a few stores around my area and looking at the contents almost all of them contain "various sugars", although it's very low down the ingredients list. From what I understand cats can't taste sweet in their food, so there must be some other reason as to why all the manufacturers add it, but can anyone who knows more about this please tell me what that reason might be? Also, while tapioca is not a cereal, am I correct in understanding that most vegetable ingredients are to be avoided? My main concerns are cat diabetes and dental problems cause by the sugar/tapioca.

Really hope this doesn't break the medical advice rule, if it is please help me adapt it to make it more appropriate.