Advantages of payment processors for ecommerce website.?

[Jake]

It's better when you are paid.

Consumers expect immediate gratification, particularly in the case of digital download products they expect immediate automated acceptance of a card payment, a phone in payment scheme adds delays and requires 24 hour staffing.

Some small operators can't qualify for merchant accounts with a major credit card payment processor and have to resort to using a service that may charge additional service fees to handle payments.
While a large ecommerce site would setup their own payment page with SSL certified https: encrypted pages, some smaller operators send buyers to a page supplied by their payment processor.

These days with mobile credit card scanner services like Square, virtually anyone can accept credit cards for a fee of around 3.6%.