I suppose some of that may be down to the difference in the value of the change. It was worth about 2.5X what it is today back when I was working convenience store night shifts, so people might have cared more about getting it correct.
Even more, people at Starbucks are paying $7 for a cup of coffee, so they're clearly not very price-sensitive. If the customer doesn't bother to look to see whether they got the correct change, should the cashier waste everyone's time getting it right? I think yes, but I could see where people might disagree.
I know people at the convenience store got pissed when they got shortchanged, which is why cashiers who couldn't count change out got fired pretty quickly. They might last longer at Starbucks today. Especially since most customers don't pay with cash.