It’s not about keeping your number, but having the primary account holder’s name show up. Quoting one example from the article: That realization came publicly

It’s not about keeping your number, but having the primary account holder’s name show up. Quoting one example from the article: That realization came publicly for Derek Forbort, a 30-year-old hockey player for the Boston Bruins, when he was on the Boston sports radio show Zolak & Bertrand. … Bertrand asked who “Mary” was, referring to the name that popped up on caller ID. “Um, no comment on that,” Mr. Forbort said. After more pressing, he copped to being on the family plan—Mary is his mom—but said he pays his portion of the bill. After he hung up, the hosts razzed him, wondering if Mr. Forbort, who makes $3 million a year playing defense, still got gas money from his folks. Mr. Forbort said later the radio show caught him off guard, and he didn’t realize caller ID “was still a thing.”