IOW, your SIL’s family will starve the first week she loses her job. The kids don’t have milk for their breakfast if she gets sick on Sunday and can’t get out of bed, or there’s a flood, snow storm or other natural disaster or the car won’t start. There’s a reason pantries and freezers were invented.
Unfortunately, there are many out there with the same mind set.
How sad to know you have to shop so often. All that time wasted on the road (an hour here), and all that time pushing a cart going up and down the same aisles week in and week out. Granted, I’ve been going weekly during this virus thing but normally it is once a month or six weeks. Saves so much time and effort.