The reality is that not everyone has an acess to the internet and not everyone has knowledge about it. We can't always rely on the internet since it's not always available specially if we're not reachable by the internet service provider. No matter what happen, physical currency is still needed specially by small people who can't or doesn't have a time to connect to the internet.
The worst problem here is that they don't even know how to use or even access the internet. In our country, there are still a lot of people that can't use a mobile phone correctly. We are still in the phase where phones are still new, there are still a lot of poor people here. If they can't even use these technologies, having an ISP does not matter. That is why fiat or physical currencies are still needed, it will be a long time before these people keep up with the technology.