> Do people's purchase habits follow the natural seasonality of the product anymore?

Depends on the store I'd wager. We have a store here (Ametller Origen) that sell things they cultivate/make themselves "nearby" (in the same region, and among other things they sell too) and sell in their own retail stores, I'm guessing most of their customers do indeed follow the habits of seasonality as lots of stuff isn't available outside of the seasons.