We don't all have cars. I once got a taxi to bring home a load of shopping from Tescos when I bought more than I meant to and was feeling a bit fragile - it added £10 to my checkout bill. If I'd been unable to walk to the bus stop and taxied to the supermarket as well it would have been another £10.
Getting a delivery from Tescos costs up to £5, with another £4 added if the basket value is less than £40. Shopping for one it is not easy to make it up to £40 each time. Adding £9 delivery to £25 or so is an expensive way to shop, so I only do this at intervals, when the tins and jars and potatoes and packs of toilet/kitchen rolls are almost finished.
Using a bus pass means that transport is free, and I can buy as little as I need. If I feel like it I can also go to Lidl (two buses each way, which would cost me over £6 in fares) - and shop more frequently which means fresher and healthier food, more exercise, and a chance to talk to people at the checkout, the bus stop, neighbours along the road etc. all that keeps me physically and socially fitter and less likely to cost the NHS money.