They can be turned down to 30 pounds, but that doesn't mean that they should be. They should be shot at a comfortable poundage, appropriate for archer and game, and at one that suits the arrows well.

I suspect (and this is my own pure specuation) that the reason you have high end bows with low end draw weights is to accomodate ladies, as well as older hunters, or those who may have endured shoulder injuries but still want the performance and technology a high-end bow offers. I'd much rather shoot a 50#, high end, well made performance bow, than a 60# bow that I didn't like or shoot nearly as well. Especially when it comes to rehabing hurt shoulders.