With the possible exception of "privacy", that use case is already solved by bank transfers all over the world - in particular, check out India's UPI:
https://bam.kalzumeus.com/archive/bank-transfers-as-a-paymen...
https://bam.kalzumeus.com/archive/bank-transfers-as-a-paymen...
It can also come in the form of something like paypal. Paypal could reduce their rates to almost zero. If everybody then uses paypal we achieved our goal. But for that to happen paypal needs to become a monopoly, and once it is it has no incentive for low prices.
Note: I meant privacy as in private for consumers. With bitcoin everybody can see all transactions. I (and most people) don't really care that the government can see your transactions for tax and anti-fraud purposes.