They are an alternative to chicken nuggets that could fill another day on the school lunch menu and also for parents whose kids would only eat bland brown things or who didn't want to cook. Almost no one really intentionally eats them.

People who wanted fish and wanted it simple would go with canned sardines, canned tuna, or canned salmon made into salmon patties. Those who wanted fresh fish and were willing to cook would just get fresh fish and cook it however they wanted.

How often do you see fish sticks on a gourmet restaurant's menu? If you ever see it on a restaurant's menu, it'd be in the "kid's meals" section of a cheaper restaurant, next to or in place of chicken nuggets. If people actually wanted them, it wouldn't just be tucked away there.