In 1990, three years after retiring from the Court, Powell told a group of New York University law students that he considered his opinion in Bowers was an error. "I do think it was inconsistent in a general way with Roe. When I had the opportunity to reread the opinions a few months later I thought the dissent had the better of the arguments." However, Powell believed that the case was one of little importance and spent only thirty minutes thinking about it.This, as hilzoy says, is why it's important to have a diverse Supreme Court. If you're not a gay person, you might not think that the right of gay people to have sex with each other is especially important. You'll probably still think that your own right to have sex is very important. For many of the issues that come before the court, there's no explicit ranking of rights to be found in the Constitution that you can interpret to figure out what you're supposed to do, still less one that explains how to weigh these in a particular situation.
So people are going to fall back on their own experiences. (People unusually gifted with empathy may be able to understand the weight of their decisions in the lives of others very much unlike them, which is why Obama is right to prize that quality.) But this is why it's good to have people who have had a wide variety of different experiences on the Court.