Sure you could let Visa do this (as they and Mastercard handle most online payments now anyways), and it would probably work as well as Visa/Mastercard work now, but for some people that is not good enough.
1. Differentiate clearing (telling you you now have some money) and settlement (you getting the money you "have"). For Visa and Mastercard the latter takes days or more.
2. Permissionless means that you don't need any entity's permission to transact. Visa and Mastercard definitely require permission, and on occassion don't give it for various legal but "immoral" things like porn, Wikileaks, and who knows what in the future.
3. Borderless is kind of similar to permissionless. As soon as you bring in legacy behemoths like Visa into it, this kind of goes away.
4. With decentralization, fees are determined objectively (you pay to get in, and if there is enough demand, regardless of price, blocks are full). A monopolist would charge as much as they could get away with, sometimes even if that means no transactions are being performed.
---
I would say that with a Visa(like) company, you definitely lose 2, and 4 will probably have some bullshit involved.