Yes, there are. Some people just like to wear. Not me, but those people are out there.
Amusingly one literary reference is in John Irving's The World According to Garp. Garp's neighbor is revealed:
Cushie had also told Garp that Bainbridge was still inclined to wear a diaper—perhaps, Garp thought, because her family still insisted on calling her Pooh.
“Well,” Cushie said, “I don't see what's wrong with it. She doesn't use the diapers, you know; I mean, she's housebroken, and all that. Pooh just likes to wear diapers—occasionally.”