It's much more convenient if you have a system for doing groceries. Compare visiting 2 stores in walking distance (~ 90 minutes total) vs putting a predefined list into your basket and optionally add or remove a few items (~ 10 minutes).
You can easily do that in Germany with some traditional supermarket chains, e.g. REWE, create your online basket, then when ready do the 5 minute walk to pick it up without dealing with the supermarket confusion.
