2.9% plus 30 cents (in the case of Stripe) is pretty darn expensive, your effectively paying 9% in fees on a $5 transaction. Better processors have slightly lower percentages (~2% & $0.05 to $0.10) but they're often a pain to work with and have a variety of hidden booyah fees that drive up the cost (PCI compliance fees, statement fee, requiring a wired internet connection for a credit/debit terminal).

Large chunks of the US still operate primarily in cash to avoid these fees and presumably some taxes, SoCal is a good example of an area where using credit is often discouraged (even Kroger is not accepting Visa!).