In most cases, it's not pathetic, and it's certainly not unnatural. Before the government decided we should no longer be personally responsible for our elderly parents or our children with young families, families remained together, often forever. Certainly it was common for men to live with their parents until they were married and often after, until they either could afford their own home or inherited their parents. Young couples who are getting on their feet often will remain at home with their parents for the same reasons...my sister and brother in law, both working attorneys, spent several years living in the basement apartment of his parents' house before building their own home on the family homestead. When his uncle lost tens of millions of dollars and went bankrupt in the 70s, he moved his entire family to (then) Taiwan, where my brother's family was living during the time my brother in law was serving in Viet Nam (they moved there so they could easily see him on his furloughs).
My son currently is living with his wife and baby in the basement apartment of my sister's home. He's attending school and his wife works full time. They aren't pathetic, it's not unnatural. It's the way families support upwardly mobile members.
My daughter-in-law is seriously considering coming to stay with me if my son is deployed to Iraq and her time in the military is up. Fine by me. My elderly mother (who currently works full time) will eventually come to live with me as well.
And I've lived with her off and on during my adult life, with my children, when times called for it.
What is abnormal is bolting from the nest at 17 and never going home again, expecting the government to look after your folks in their old age and fund you if you're too much of a loser to work or you get knocked.