Visa and Mastercard handle roughly 7000 transactions per second. Solana's chain (as an example) is among the highest performing and can handle north of 50k TPS.
Edit: Please challenge my position and make me think. Votes are pointless, but being proven wrong is a learning experience.
We looked into the option of accepting cryptocurrency as a payment method but came up against too many obstacles. Without being able to prove the provenance of client funds we would be at risk of breaching "proceeds of crime" / anti-money laundering regulations.
And while the value of cryptocurrencies bounces all over the place and makes it impossible to budget, even stablecoins present problems. While they are pegged to something, the question is to what. Those pegged to precious metals such as gold or silver were a no-no, and even those pegged to the dollar present a problem. (As an aside it obviates one of the cited advantages of bitcoin - as a hedge against monetary policy-driven inflation). The question our board came up with was, if the currency is pegged to the dollar, why not just accept dollars? At least with established currencies we can buy currency hedging. With stablecoins, we'd be looking at specialist forex hedging, or messing about with futures. The board looked at the cost-benefit for about five minutes before they threw it out.
Lower transaction fees, no chargebacks, and being able to serve international customers effortlessly.
Agreed that accepting cryptocurrency doesn't have much appeal yet, and pitching it to a board would have mixed outcomes. I don't have any answers on provenance, and am not sure how this is being handled by the large amount of companies that currently accept it.
While adoption is low, I think most companies are opting to settle transactions to cash. This is probably the safest choice for now.
Now that I've argued for it, I also think accepting cryptocurrency doesn't fit everyone's business model yet and isn't always the best choice for some companies.