When Jeffrey Zachary, a bus driver from Canton, Ohio, said he was going to New York City to help out during this summer’s transit crisis, his friend warned him not to talk to strangers. “My buddy said, this is not the type of city where people will be so receptive,” Mr. Zachary recalled.

But conversation is fundamental to Mr. Zachary’s character. Last month, as a couple boarded his bus in South Orange, a New Jersey commuter town, he told them that their coffee sure smelled good. The next day, they returned carrying an extra...