Can someone from Xi'an explain this phenomenon? Everyone on the street has a box.

These green bags are really something. From Sajinqiao on Muslim Street to Miaohou Street, then to Zheng Street and Chenghuang Temple, these are everywhere. Curiosity got the better of me and I tried them. ✓ Mung bean cake You can taste the rich mung bean flavor. It's soft and sweet but not greasy. It melts in your mouth. The red bean, jujube, and black sesame flavors are all great! ✓ Mung bean pie You have to eat it while it's hot. The crust is crispy and crumbly, and every bite is full of filling. Locals in Xi'an often buy them. The old brand is stable. It's perfect for travelers to bring back as a gift.