I think it's just that everyone is close enough to a supermarket, it's easy enough to just go there on the way back from work, or just pop to the supermarket. It's not worth paying to get someone to do the groceries for you.
I don't think I've ever lived further than a 15 minute walk from a supermarket.
I think that's also true in Europe. I've never lived in the UK, for example, but I've stayed there for six months while working. Food delivery was very common in London.
At the time, there was no web interface and you had to make a phone call. Still, it was pretty common.
Curiously, when I was really young (1960s America), I remember a grocery store that delivered to our house. We even had a diaper delivery/disposal service, but I digress. I'm not sure if it was a local thing, nor am I sure when it stopped. I do know that it existed in two different localities, because we moved a lot. (Military family.) I'm pretty sure it wasn't always just a grocery list, but that they had meals that came with a recipe card and the ingredients. The recipe cards still existed when my mother passed away. I have no idea if they still exist. I suspect not.
So, at one point, it was at least in use and then fell out of fashion. Now, it's coming around again.
Anyhow, thanks for the info. It seems to be gaining in popularity. Maybe there's room for you to get in on the ground floor and make some money.
I don't think I've ever lived further than a 15 minute walk from a supermarket.