Why is it important to respect elders?

It depends, if the senior citizen is Charles Manson, not much...respect is not meant to be automatically gifted to one simply for being around a while, it is a measure of endearment to one who has earned it. At that point it is entirely subjective, some choose to give discounts, work-related favors, or simply devote a little time each week to talk with them. It it ultimately up to you.