There's a stigma against just doing something for nothing, or even doing nothing and being lazy.
Italian and French grandmothers make far better food without calling themselves "foodies" and a 15 year old from those countries has better knowledge and breadth of food.
Well you should know that foodie culture in the US, like almost everything else in this country, is maximally consumerist. This explains the bizarre behavior you've pointed out.
Many of the self-described foodies I've met lacked a genuine appreciation of the cuisine they consumed. It was simply another avenue for them to moralize and project their socio-economic status in a subtle way. Subtle being necessary because this country is supposed to be one of equals.
Identity in the US is tied up not with the relationships in your life or the values that you live by but by what you consume. Food is the ultimate consumable good.