First of all, the paper. Only some billers give customers the option of turning off the flow of paper bills that come to their homes. Most still send them every month, whether you pay electronically or not. It's saving you the hassle of having to write the check and mail it yourself. Some billers, such as phone companies, will offer lower rates to customers who pay electronically and opt to have the paper bills turned off.
Paper also can still appear on the back end of the process.
If you're paying a bill electronically through your bank or other third party, that company will then have to cut a paper check on your behalf. That also slows the process, which means the payment doesn't land in your account at the biller for several days. Of course, customers may wonder why they lose float time - why the funds leave their accounts at once, when they don't arrive at the billers' until later. That float time is something you have when you mail out a regular paper check. The bank goes on to say that debiting the account immediately helps it guarantee delivery of the payment by its due date, gives the bank more flexibility in stopping or re-issuing payments on your behalf, and guarantees the customer won't be hit with an nonsufficient funds charge if he doesn't have enough money to cover the payment.