1. I always know how much cash in in my pocket. I typically carry $30-50 which is plenty for everyday transactions.
2. It's easy to budget with cash. You can never spend more than what you have.
3. I don't have to worry about paying off card balances.
4. The chances of getting a credit / debit card stolen are a lot higher than having my cash stolen, eliminating the hassle of replacing cards.
5. I support my community by eliminating the overhead of accepting cards.
6. I can easily pay individuals instantly without having to worry about what service to use or delays in transferring from my bank to theirs.
7. I maintain my privacy.
I'm not even considering the downsides of using a phone for payments (lost / stolen / broken / dead battery / borked update / bad UIs).
All that said I use a mix of cash and cards. Cards do have a lot of consumer advantages (cash back, disputing transactions, etc). Don't pretend that they're far superior to cash though. Both have their advantages and disadvantages. The loss of privacy is a HUGE problem with electronic payments.