We can take 1btc and buy a 2bed apartment in the heart of any significant part of the world. We can take 1bitcoin and start our own business. Bitcoin was never built to allow one to buy groceries.
Think of a situation where you have a few coins worth 400 thousand dollars or more. A wealthy person like you can still buy groceries with Bitcoin just like people did in the old days.
A wealthy recognized individual had a store tab that would get paid every month. They wouldn't have to carry money around every time. They'd go to a store take what they wanted and get it signed to the tab.
It's also possible to use your address as an escrow. You'd get a wallet that would lock up 1 bitcoin and then a third party processor would cover all your payments in fiat money. Once those bills reach 1 BTC the escrowed bitcoin would be sold by the processor and you'd have to recharge the account.