As someone who is about 2 hours from my nearest bank branch, I have trouble with quickly getting cash for a purchase. One of my recent purchases for about $5K was in cash because the seller would not take Zelle or Paypal. I had to use an ATM multiple times/days to get all the $20 bills (250 of them if my math works). The seller complained bitterly about that too.
It's the sellers prerogative to demand cash.
Perhaps in another 10 years people will come to learn that Zelle is a bank-to-bank wire transfer and be OK with it. Until then cash is king, even in small bills.
