Simple google search yielded surprisingly interesting answers:

http://www.ukskeptics.com/article.php?dir=articles&article=why_people_use_alternative_medicine.php

The tendency is that people are more likely to use alternative treatments the more educated they are. The level of education a person has attained is probably the the best indicator that a person is likely to use some form of alternative treatment.

Being intelligent or well educated does not mean that a person is going to think more logically; in fact, it often results in them becoming better at defending and justifying their irrational beliefs.

Unfortunately, conventional medicine is not perfect; people do have bad experiences with it. This can lead people to distrust conventional medicine and sometimes shun it. This is only true of a small proportion of people, but the big danger for them is that they are more likely to use alternative remedies as their primary source of healthcare. These people often decide to take full control of their own, and possibly also their family's, health. The consequences of this may be damaging, even fatal.