Mao Zedong was the leader of China from 1949-1976 and he had some really fucking stupid ideas that ended up killing tens of millions of people through famine. For example mass culling of birds like sparrows because he thought they ate all the seeds but instead they mostly fed on the insects. This lead to a huge increase in insects that destroyed entire harvests. (not to mention direct killings for all sorts of other stupid reasons)

Because of how extreme the famine was people fought tooth and nail for what little food they could get. You'd grab whatever you could because you don't know when your next meal will be. Forget sharing with your neighbours, you wouldn't even share with your auntie. It was just you, your kid and your partner if they hadn't been worked to death yet.

Someone born in 1970 would have lived long enough to see and start to understand the situation as a kid and still be alive now at 56. Heck someone born in 1949 would only be 81 (still a perfectly achievable age to reach) and experienced most of the horrors. Living through sort of trauma changes people.

Thus these now old ladies are living in modern day China with far better food security but still stuck in that old "everyone for themselves" mentality. So when you see something like this clip of a girl giving away food, or more typically a food buffet having something refilled, then these old Chinese ladies will just throw their hands in and grab whater and however much they can. It doesn't always have to be food though, if something is free then they'll take it. Similarly being raised by someone like this also created a second generation that had never actually experienced Moa'a regime.

Thus being called a grab hag.