I find it hilarious that you think everyone is using bitcoin to buy their starbucks coffee. It's a terrible currency to use with any frequency especially for small payments. 99.9% of the world is using fiat.
Discussion
Have you ever heard of lightning network? I do pay for a coffee or a lunch on a regular basis.
For example, here in Czech republic, thousands of restaurants and coffee shops accepts payments via app called “qerko” which accepts LN payments.