My adult boyfriend (38 M) seems to have no desire to move out of his parent’s basement or get married.

His mother is on my side. She wants him to get married, to have children and to leave the nest. She's frustrated as well. Sometimes he mentions getting therapy, but he never makes an appointment. What is going on. Why does he have no desire to get married and grow up? He has a well paying government job with benefits. His siblings never went to college and have both bought homes, gotten married and have children.