There is nothing less appealing to the girlfriends and wives of grown men than seeing their boo wearing another man's name on his back. She probably looks at the guy on the field or court and realizes he's 50 times the man you'll ever be, with a bank account to match. If you were 6'3" and could throw a ball 70 yards, would you have an ounce of respect for the grown man wearing your name on his back? No, absolutely not.
After the age of 11, wearing a jersey is pathetic.