Apparently the grocery shopping habits of UK/European consumers is considerably different than North Americans and so something that works in one market doesn't necessarily translate across the Atlantic.
In the UK, my old supermarket had a couple of aisles of prepared chilled meals. Lots of variety, and a lot of it was pretty good quality. You just don't get that in North America, and apparently it's because NA consumers tend to go to the grocery store once per week, where in the UK it's multiple times per week. So over here the convenience meals are frozen and icky. Blurgh!
Similarly, I could imagine the economics of delivery would be vastly different. The UK has tightly packed cities with high population density, meaning your delivery vehicles don't have far to go between stops. NA has large spread out suburbs with lots of driving to get anywhere...
For you maybe there is no difference between having time and desire to prepare food and having willingness to go to the site, but you aren't the whole market.
Outside of the multitude of 'walmart' farmers' stories, I remember rather recently reading of a lady who made salsa, who made cents per jar sold on an item that cost a few dollars to the consumer.
This means there is heavy markup at someplace, which I suspect is at the distribution and delivery. It was evident to me when, to make a pizza of high quality with many toppings, it ended up costing me more than even the local chains charged (greatly reducing the 'economy of scale'). There are billionaires in this particular realm, Walton's excluded, see Richard Cohen.
This also makes me wonder if then, distributors like C&S, Sysco, or Gordon Food Service would get into the personal delivery game. In the end, it seems rather silly to deliver goods twice.
Overall it is a challenge for a parent though, so I'm not convinced that many won't just stay at home and order food from an app with the kids watching TV.
I guess most people using the service order groceries at the office and pick them up on the drive home.
I'm not in their target demo because I don't have kids and my life isn't that busy, but i've been surprised at how busy the designated parking spots seem to be whenever I go to one of their stores. I've just checked their website and there are no fees for using their service as long as you spend $30.
You become much more financially responsible and less likely to pay for luxury services (for yourself) like HBO, Spotify, Netflix, Gym membership, high lease car payment etc after you have kids.
The local Walmart here experimented with something similar a few years ago, not using Uber but using customers at the store. Shoppers could get store credit in exchange for delivering orders on their way home. They don't do it anymore so it must not have worked well.
I've got a ton more options on how to procure food.
I think grocery and other same-day retail delivery is going to be huge, even if it seems a little weird and unnecessary at first.
It's common here (a poor part of the UK) for people to take a taxi home from the supermarket. So I can see it could work if all the supermarket's didn't already do delivery as they do here.