There should be a variety of options: free L2 charging while you shop, and fast charging for a fee per kw. L2 makes more sense if you arrive with relatively high state of charge and get enough juice so that you arrive home with the same or a bit more of charge than when you left home. However, if your state of charge is low, connect to a DC fast charger. That will fill up your battery while you shop.
Now, vendors must begin to think of ways to discourage leechers who live nearby and don’t go shopping but still want to take advantage of the free charge without having to shop or pay for the charge. Perhaps a QR code printed on your store receipt to be used as a voucher so your charge is free. So if you don’t have the QR code, you just have to pay.