I don't get where "easier to transport via rail" comes from. The instant you have a post office, you do want some sort of roads, and the number of rails and switching you would need to get to even some of the distribution centers spread across various supermarkets is a big ask!
That doesn't mean every single last meter needs to happen via truck (lots of deliveries in urban areas can happen via foot or scooter) but ... at one point you need to get the 200 cartons of milk to the supermarket.
No one is saying “replace roads with rails”, they’re saying ship more things by rail up to the last mile (e.g., trucks take goods from rail depot to local markets). Today, much freight is shipped on highways.
That doesn't mean every single last meter needs to happen via truck (lots of deliveries in urban areas can happen via foot or scooter) but ... at one point you need to get the 200 cartons of milk to the supermarket.