It's all the hassle of getting to the supermarket, finding a parking space, making the kids wait while you sort out shopping bags etc, going round looking for things you need whilst the kids pester you for stuff you don't need, stopping them getting in the way of other shoppers, queuing up with bored kids, paying and packing, schlepping out to the car and putting the bags in, returning the trolley.
Jeez, if that is your experience, that is sad. I find parking space in less than a minute (at the back), we walk to the shop with DC being carried where need be, the bags are already sorted as all in one bag anyway, the DC know better than to pester, shopping at ALDI or LIDL means queues are short anyway and the rest is part of food shopping anyway?
In the meantime, we talk to our DC, have a good laugh, get them to help us fetch stuff/ put stuff in the trolley and are in and out of two shops within three quarters of an hour max total.
But then we teach them manners and have rules about pestering/ running around...