People are defensive of changes outside of culture. "I am a vegetarian" is a personal choice; "we're all vegetarians now" is a social shift.

In 2004, my wife discovered that wheat gives her eczema. She's an ardent baker; suddenly the constant cracks on her hands and lips made a lot of sense. So she gave up wheat back when it was a few random celiacs and her. Then a whole groundswell of people also gave up wheat (for good or questionable reasons; not getting into that here) and over time things got a lot easier. In 2005 I had to call ahead to the weird bakery that ran out of the back of a tea shop to get enough gluten-free bread to make stuffing. In 2013 I could buy Udi's at the local supermarket. Now, I go out to bars and have to be cautioned by the servers "you should know that one's gluten free" when I order a beer.

People like to eat what tastes good and what they can afford. Food is much trendier than you think. Last week I was walking around looking for chocolate wafers for a cheesecake and found myself saying "holy shit, Snackwells" when I saw some of those wretched little devil's food cookies. I hadn't seen them in a decade; when I was in college they were half an aisle.