Are people in those neighborhoods willing to forgo the hundreds of vehicle trips a month that they will create via their Uber/Lyft/cab trips and Instacart, Amazon, Chewy, Doordash, and Uber Eats orders? Simply outsourcing those car trips to someone else, and leaving them nowhere to stop in the process, is a hypocritical pipe dream.
Walkable neighborhoods existed for millennia before these apps were invented. People just walked to a shop a block away for the things they needed. Not sure why you think that you have to "outsource those car trips to someone else" when many neighborhoods already don't need car trips at all.
I live car-free in the DC metro area. I ride a bicycle with a rack on the rear for attaching bags, I have a collapsible shopping cart that I can take on the bus, and I have a dolly for moving heavy objects short distances. I've gotten a lot done with them.
Those days are gone because no small "shop a block away" can compete with the behemoths of Amazon, Instacart or major supermarket chains that deliver, or cloud kitchens with DoorDash or UberEats, not unlike how American fast food chains and Starbucks crowded out a lot of former native mom-and-pop cafes and restaurants.
What "existed for millennia" only had to compete with nearest such other small business in each direction. Now, they're competing with the world's supply chain.
Just look at a traffic cam in any "walkable city" where vehicles still run and count the brand names crowding the streets doing trips that just didn't happen even 20 years ago.