Why do people not have their change ready when they get on the bus?

They don't see it as a concern. A lot of elderly women wait patiently until their groceries are scanned and sacked before they will began to write out their check. Even after they have delivered the check, they may linger for several more minutes of small talk with the clerk. My being in a hurry is no concern of theirs, they have a lot of time before their next soap opera comes on.