the NSCA and other personal training organizations dont reccomend many supplements, mostly for liability reasons. Why? Because people have blamed creatine for various maladies, usually due to coaching incompetence and overtraining, poor diet, inadequate water, etc (examples wrestlers deaths due to dehydration and hyperthermia- tried to blame creatine- when running in super suits, sauna and inadequate water intake and extreme calorie deprivation to "make weight" were in fact the cause- as found by the coroner.)
in numerous studies creatine has proven to be a performance enhancer. particulary exhaustion and 1rm studies.