The US payment networks are also incredibly robust with some fantastical operational guarantees. I cannot recall the last time I couldn't get an online authorization at a merchant terminal. There are rooms of people monitoring these things like a hawk 24/7/365. Imagine being called by your ISP proactively when they detect >.01% packet loss on your line. That was my job for an entire year. Calling banks on the phone in the middle of the night because we think there might be an issue before there actually is an issue. Statistically speaking, this is one of the most certain things in the life of a typical American. Visa alone processes a quarter trillion (10^12) transactions per year. We've got a lot of samples that say the system works really well and might be worth the cost.
You can point to regulation and artificial moats for prohibiting competition, but it's genuinely a difficult problem to solve, even if you can do it purely digital. Trust is the most challenging element. I think moving cash, checks and other paper around is easier in a lot of ways.