Food counts, let me explain you why.
All games that require resources to build troops, army etc., they all require one typical army feeding resource. In this game we have iron/gold/food. Check section called "train troops". You will see that all troops require less food than iron or gold. Its because you have to build big army to achieve something, solo or with your team, thats why food is very valuable resource.
The question is, why you think about this question ? Its because you see massive amounts of production per hour. You can produce 100k food per hour but only 2-3k iron/gold. Then first question is, does food have value ? Yes, because in the end since you build, build, build, you keep getting less and less production, untill the day when you have negative production. In this game you are lucky because you don't have to feed your army, I mean your units dont starve when you produce -10000000000b food and have 0 in your barn. Its because plarium needs money, they have such things like resource packs. And when you see food packs, you have unlimited purchases of them. Why ? Because you have negative production, or one day you will reach it, so if you want to keep building more, you will need food. That leads to an answer why we have limited raids aswell, resource transfering limits between league members or w/e too . And in the end it makes food very valuable resource.
What you send to battlegrounds ? You send troops, troops that you have built with iron/gold and also food. Those 3 resources are fundamental things, and its logical.