In the world we live in, it is all about who looks the best. This is also true when it comes to trainers. Sure, you don't have to have the face of a model, and a body of a greek statue come to life to train people, BUT that is usually what others want to go to.
Girls want to go to a hot guy trainer, *usually* hoping in the end, she will end up getting a guy like that in real life. Guys usually go to the better looking trainers thinking they will get the type of girls he does, or the type of girl she is (if the trainer is a woman). Think about it, who would you want to train you? The balding, geeky looking guy (even if he does know his stuff), or the confident, good looking, very well built guy/girl who also knows their stuff?
*Most* people looking for a trainer aren't really looking to change their lives, work really hard, or go at it like most of us. They are all mostly looking for a quick fix, and think if they have a trainer pushing them, they might just be able to do that. Some even like that safety net, because then if they fail, then they can blame someone else besides themselves.
If you are confident, have a good personality, and a good body, then you can make some good money as a trainer. You do have to work, it's not gonna be all fun and games. You really do have to help these people. Good luck...