"If music be the food of love, play on" Shakespeare wrote in Twelfth Night. Which is beautiful - and interesting. He talks about music being the food of love, whereas what I see as far more common is that food is the expression of love. Many of us grow up in families where food is not food. Food is much more loaded and important than that. In many environments food is the messenger of love. Food is the physical manifestation of love. Food is love.
Particularly when there has been a previous environment of scarcity (for instance growing up with rationing), it creates a situation where food is a currency of more than fuel. Food is precious. Food shows you care. That you put someone else's needs before your own.
And you must never, ever waste food.
This food scarcity mentality can subtly influence us all for generations. If you grew up in a home where this is the unspoken philosophy, then food may come to represent love for you. Saying yes to second helpings = demonstration of love.
Praising the cook = demonstration of love. Bringing a plate = demonstration of love. Which has much to commend as a strategy for caring and co-operation.