Let alone the "what looks good today?" or "what's on sale today?" method of shopping!
Even packaged goods are tough. When I'm in a store, I know quickly which product I want. I may not remember the brand name, but I can scan the shelf and find it.
Online, I have to sort through a myriad of options, not to mention sizes and variants.
BBQ sauce, for instance, returns 58 results on Peapod. Sweet Baby Ray's, which I like, is 22 of those. There are 13 different variants (original, hickory & brown sugar, honey, buffalo sauce, sweet'n spicy, honey mustard, honey teriyaki, sweet teriyaki, sweet vidalia onion, maple, sweet chili glaze, honey chipotle, no sugar added) and 7 different sizes (14oz, 16oz, 18oz, 18.5oz, 28oz, 40oz, 80oz).
Holy crap!
I know what the label looks like, and I know the bottle is about yea-big. The images online are 200x200... I can barely SEE the label.
Then, what if what I want isn't in stock? Is it going to appear on the page? Am I just not going to get it? Would I get a substitute, as I might if I was in the store?
By the time I do that mental exercise for 50 items, I might as well drive to the store.
These are hard challenges.
One thing that might make a difference is integration with club cards. Giant knows what I buy down to frequency and UPC. Why haven't they done better integration to link my in-person buying with encouraging me to buy the same items online?