^^^ I do understand where you are coming from and if I was too add another 30 pounds to my squat next time I went to the gym (without getting injured) I would surely need a belt. But I feel I am working just as hard now and getting the same gains without the belt, as I would adding a belt and 30 pounds to my squat... I also see what you mean about power lifting, but the way I train (and a lot of others) has little to do with the training theory of power lifting Do everything the body is capable of to lift the most it possibly can. Anyone aiming to be a powerlifter or win a powerlifting competition would be foolish to NOT use a belt.
But for most people and particullarly in terms of conditioning for boxing, aiming for high poundages comes second to getting every part of the body in the best shape it can be, and a belt definetly takes away benefits to some of the muscles that help support the weight (and your body) during a squat...

I guess we could go on discussing this forever, But if you'll agree, we can summarize by saying:
Wearing a belt DOES have it's advantages in a lot of cases, and certainly wearing a belt compared to having a back injury is a very easy choice for ANYONE. But it should also be acknowledged that a belt does have some disadvantages and it's up to the individual to weigh these up and decide which best aids them in acheiving their goals.