I will say that I’ve been able to bring 3-4 grocery bags onto a bus, which is enough to last me around 2 weeks. I’ve done this fairly consistently (basically whenever it’s too cold/snowy to bike) for the last couple years. It might not be possible for a family without more than one person making the trip, but for an individual it can definitely work.
I completely understand that, and I know that’s why a lot of people need cars. I was primarily responding to the parent comment claiming that it wouldn’t work for anyone because it’d be impossible to bring enough groceries with you on the bus/train.