Cash is easy for simple informal transactions (e.g. garage sales, farm stands and the like) and where connectivity is poor or nonexistent.
A lot of the alternatives involve unnecessary infrastructure (e.g. PayPal etc have various controls to block money laundering, which isn't the purpose of your once-a-decade garage sale) or are siloed, making it hard to quickly do business with someone who has a different brand of phone or doesn't have the right app installed.
And asynchronous transactions are hard (I used to buy a newspaper by leaving a quarter on a board and grabbing a paper...and this setup was next to a busy subway station!). And farm stands are often simply goods left out on the honor system.
A lot of the alternatives involve unnecessary infrastructure (e.g. PayPal etc have various controls to block money laundering, which isn't the purpose of your once-a-decade garage sale) or are siloed, making it hard to quickly do business with someone who has a different brand of phone or doesn't have the right app installed.
And asynchronous transactions are hard (I used to buy a newspaper by leaving a quarter on a board and grabbing a paper...and this setup was next to a busy subway station!). And farm stands are often simply goods left out on the honor system.