99% of the time. Toby sat up unassisted very late, so he was a floppy boy for months and months. I needed the padded shopping cart cover so that I could shop with him! (He hated carriers and outgrew his infant seat at 3 months old.) I have a BuggyBag, which also comes with a pillow that was great for propping him up when he was younger.
Now at 20 months I use it if he's going to eat a snack (to contain the mess), or if it's raining/cold. It folds into itself and zips closed to a duffel bag shape. I always park next to the cart corral and bring a cart over, put the cover on, and put him in.