It's a pity that the UK used to have a huge fleet of low-speed electric doorstep delivery trucks, devoted to milk and groceries; but they were all phased out just prior to the internet era.
I imagine how good that bike fleet would be today if they added electric assistance. Sure bicycles might not be great for the final mile delivery of someone's Amazon order of 50litres of mineral water but that is the point.
I think it's more likely that they moved to trolleys for cost, and gave the excuse that it was "health and safety".