Some people would rather retreat into fantasyland than deal with reality. It certainly feels safer. No threat of rejection or being hurt. No chance of experiencing real love or fulfilment, either. This guy has committed. But not forever. One terrible morning he's going to wake up and feel as empty and as lonely as he did before he started this thing. Realize his whole life is wrapped up in a illusion. Nothing in their relationship is real. And he can't ever go back and choose another path.