The biggest part of the network (imo) is that it is also a payment processing network. You buy something with BTC? You can then repurchase that same amount of BTC with USD.
Or you can hold zero BTC in reserve, and only buy BTC when you need to spend it.
On the merchant side, you can instantly cash out to USD, making it a simple transaction over a payments network, using BTC as a unit of value specifically to transfer.