I think there are many different reasons why hips go bad. My friend who referred me to Dr. Gross had one of her hips resurfaced 7 years ago, and has no problems at all with the other hip. When I had my first appointment with Dr. Gross, which was for my right hip, he pointed out that both of my hips were in bad shape (although at the time, I had not noticed any problems with the left hip). I asked him how come I have this problem, when most of my close relatives, like my mother and father, uncles, aunts, etc., lived well into their 80's and 90's with no arthritis. The problem is that my acetabulum is abnormally deep (something I was most likely born with), which causes abnormal wear of the joint. Per Dr. Gross, virtually 100% of people with this problem will end up bone on bone in their hip joint if they live long enough. My mother was quite upset when I told her about this. She is 97 and has no hip problems.
This reminds me of a story my horse vet told me, after I told him about my hip problem (he noticed I was limping and asked my why). He told me his grandmother had pains in one of her hips and he took her to the doctor. The doctor told her her hip was worn out and needed to be replaced. She asked him why. He said, well, Mrs. XX, that hip is 87 years old and it is worn out. She said, doctor, my other hip is the same age, and it is just fine!