I agree the snow isn't a reason to not bring a car, but I do live near the end of the B line without a car, have for almost 9 years, and it's fine. The trains go to the grocery store, and I use Zipcar to get out of the city. Some neighborhoods it's a nightmare to have a car so it has to really be worth it, this is not one of them, so it does come down to personal preference more, but I wouldn't say it's "really hard to grocery shop".