An interesting article at houzz.com examining the psychology of man caves:
"Calm down, ladies. When a man wants his own space in the house — be it a cave, garage, bar, media room, billiards hall, woodshop or bowling alley— it’s not a red flag indicating that he's rebelling in your relationship, trying to avoid you or shirking social commitments. In fact, having one’s own personalized space is actually necessary and important psychologically for everyone.
“Space is very important for regulating emotions,” says Sam Gosling, a University of Texas at Austin psychology professor and author of Snoop: What Your Stuff Says About You. Gosling studies how space is a powerful mechanism for evoking our emotions, and he’s seen firsthand how having your own space, decorated by you alone, can positively affect emotional well-being. “It’s incredibly important to be in one’s own space and resonate with who one is,” he says."