This is a convenience for those who don't live paycheck to paycheck. Many families, myself included, are, at times, forced to pick and choose what to pay on time and what is going to have wait a week or two. Living beyond my means? Perhaps, but I'm hardly the minority.
That's a great point you make. Why can't your electric/phone/water company allow you to make those choices online? After all, they want you to pay the bill, but they'll take 'at some point soon' rather than immediately, over never.