I doubt the last mile efficiency is a big factor here. I suspect that the real optimization is in the longer parts of the route. If you're shipping something a

I doubt the last mile efficiency is a big factor here. I suspect that the real optimization is in the longer parts of the route. If you're shipping something a thousand miles to get to a customer it makes sense to have a few more trucks driving around a city if it means you have less planes, long haul trucks, etc. When I order something off Amazon and choose the longer shipping times I don't usually see it getting shipped from wherever it is to a warehouse near me and held for a couple days before delivery. Instead I usually see nothing being done until near the deadline when it ships from the warehouse. Occasionally I'll see it ship from the warehouse a few days early.