Cash doesn't have direct transaction costs, but:

- it needs to be manually reconciled at the start/end of each shift

- staff can steal it

- robbers can steal it

- it takes time to count out change (and to ensure you have enough small bills and coins)

- it takes time to deposit it at the bank

- it costs money to deposit it at the bank (even if Walmart is ok accepting cash for an iPad, I'm guessing Apple requires Walmart to pay by bank transfer)

I'm not sure about the US situation but, the last time I checked, UK banks charged 0.3%-0.5% for accepting a cash deposit from a business customer.

Yes, cash can be stolen, but cards are much more dangerous to your privacy: bank knows where you go and what you buy, it can sell this information to anyone (of course, with hashing your phone number with military-grade algorithm to protect your personal data), shops know who you are and can exchange information about your purchases along with model of your face taken by the camera at the register, MAC address of your phone's WiFi module and car plate number (of course hashed with military-grade algorithm to protect your privacy).

Also, in some countries it is very easy to lock person's bank account even without a trial, for example if person is suspected in financing terrorist or extremist organisation.

Also new cards have RFID chip in it and it can be used for example to get information about people going through the doors.

'Some countries' meaning Russia

Square recently released an infographic that supports this:

https://squareup.com/us/en/making-change

(I work for square but wasn’t involved with this project)

Never understood that. Living in the UK for example you never have to cary bills. Light wallet, so much more practical, I hate places that only accept cash.

What if every store accepted both cash and cards?

I'd be fine with this as long as you don't have to pay a fee if you're not paying cash (which is often a thing for small shops).

Unfortunately this is not the world we're living in :) it's often both cash and cards OR just cash. Berlin is a really good example of that, you always need cash on you which tricks the many tourists who come from countries were cash is not really a thing anymore.

The credit card companies make the merchant pay a fee for using credit cards - so it's not the shop's fault. That's another reason why cash is alive in America.

The bigger reason is to avoid taxes. If it’s paid with card, taxes have to be paid, and with cash, the merchant can make an extra 30%+ by not declaring it.