That is very likely often true. But there is a whole lot more to it than that. The former-SADs I know were molested as children. They developed a defense mechanism that caused them to get into the SAD lifestyle. The defense mechanism wasn't the right one, but it was the only one they could find. It took years to remove that defense mechanism and replace it with a more valid viewpoint on the world. When that happened, their SAD went away.
There are lots of reasons for SAD. In the future the most common reason will very likely be, "Hey, it's fun and doesn't hurt anybody, so why not?" It will be just another way to get your jollies.
Fortunately, for today at least, the SADs themselves are against that argument because they want the protections that come with Civil Rights law.
Shalom.