Before the fork in the 2nd half of 2017, debates were occurring over the block size, a means to process more transactions in less time for less cost. The transaction rate of Bitcoin is not very fast.
When you consider that Visa, Mastercard and American Express might have a real capacity, especially on Black Friday of handling a billion transactions in 24 hours, digital currency has a long way to go to serve as a popular means or payment.
An important measure for the consumer is the time it takes to pay for a cup of coffee. A large latte made with Ethiopian beans might cost $10 in New York City. If the consumer presents a bank card to pay in dollars, the transaction is settled in about ten seconds. With Bitcoin or Bitcoin Cash the time to settle is longer. The risk that an unsettled trade might be invalid would be too great for the merchant to assume. According to here, the settlement time for consumer transactions is around 150 seconds for Litecoin and 10 minutes for Bitcoin Cash.
Solutions are being developed to speed this wait for merchants and consumers. 0conf or zero confirmation and LN or Lightening Network are both gaining acceptance.