So they can pack Starbucks when they are busiest, costing the poor servers their tips (leaving nothing but wastes of paper for tips), and leave a $500 mess and a $500 headache. After all, they are "worldly, evil people that deserve to die" in their eyes. If they did their work in the evenings, they might not be able to shut out the busy times for those poor waitresses that need those tips.
Additionally, mornings are when they traditionally start waking people up. They work the calls in the afternoon, which is stupid (a call that was home in the morning is less likely to be home in the afternoon). Every facet has a time slot dedicated to it--street work real early, door to door in mid-morning, return visits and studies in the afternoon and evening, phone and letters in the late evenings.
And, unfortunately for the poor waitress at Starbucks, that tip money is for the Worldwide Pedophile Defense Fund.