What I find incredibly annoying is the substitution of a horrible, clunky platform like a smartphone for a fast, efficient device like a card, which only requires one device to work correctly---the EFTPOS terminal.
You can still have "scan as you go" using a card.
Using a phone, assumes that the user has installed, & is using the "App" correctly, that the phone hasn't failed, the 'phone company" hasn't picked that particular time to have an outage (or Zeus hasn't chucked a lightning bolt at the nearest cell tower).
OK, if it is a general Phone outage, the EFTPOS machine won't have contact, either, but it might be a different company.
If you really want to shop using a "device", sign up for an account with a shop, (or sign up with several shops).
Using a
real computer or a Smartphone if you absolutely
have to, you can look at what they have on their website, order it, then have it delivered or pick it up.
The downside here is that every now & then, they will stuff things up & either delete stuff from your order, not supply something & still bill you, or substitute something completely different.
I have several bottles of Mineral Turpentine, (enough for 20 years at my current rate of usage) supplied instead of Methylated Spirit. (Oh, well, it is in a bottle, has a paper label saying something, it must be the same

).
On the other hand, many years ago, I worked as a Storeman, getting out Orders, & it is perilously easy to stuff up if you are "under the hammer", as you usually are.