Very common, especially in Beijing Hu Tong (胡同, small alley) culture. Old Beijing (老北京) people ask “吃了吗” (have you eaten yet?) as we say “how are you”. It’s a common casual greeting between friends and neighbors.
Food is one of the main theme for all Chinese, regardless rich or poor, regardless of their social status. So it’s natural that food/eating would be part of our greetings.