It's an infrastructure thing. With the right regular/cargo bike or even better, an ebike/cargo ebike, 30-40kg of groceries per run is super doable.
> Nor can I go and buy a TV by just walking to the hardware store.
Do you buy a TV more than once every 5-10 years? You can rent a small van or whatever.
You definitely need infrastructure for that. Biking infrastructure in North American cities is.. not great. Definitely viable in some of the EU ones though.