Hi there UEA
Online payments may not suit all invoices, or all businesses. This is one of the reasons there is plenty of flexibility in turning this on/off either by default or per invoice.
Providing more payment options to your customers gives them the flexibility to choose the payment method that suits them best.
One example I can think of, would be If the person paying the invoice has a company credit card but doesn't have access to the bank account for bank transfer, then it would be a lot more convenient for them to pay you using the online payment method.
As the business, you would get paid faster, have better security for receiving payment, easier reconciliation and instant customer receipts.
Not all businesses will be issuing high value invoices as well. Many businesses will have a high volume of invoices at a lower value, getting paid faster and easier is a huge benefit.
Most consumers are also very used to paying invoices online and accepting the associated fees, utilities, flights and more.
You can read up all about MYOIBs online payments here