Almost Everything we do in todays world centres around connectivity through the internet.

Finance, communication, navigation, security, social interaction all depend on the internet.

Usually there is a minor disruption without internet for a few hours but with a few days
outage there would be a lot of disruption, everything above would be affected.

With banking specifically, well with their Fractional Reserve Banking practices they would
be in big trouble, people would need CASH for daily transactions for simply buying food
and fuel. The problem is that the banks would not have enough CASH reserves to meet
everyones requirements so they would have to close to prevent a "Run"
...so people would have no access to CASH or at best limited access to their deposits.