There is a tremendous amount of money to be made in so-called 'alternative' medicine today. Billions are spent every year and its popularity only seems to be increasing -- but why? What is it about alternative medicine that causes people to eschew proven, scientific medical treatments? Do you, as an atheist, use any so-called 'alternative' treatments or do you (generally) reject them as no more valid than most supernatural and paranormal beliefs?
By some estimates, the alternative medicine industry does between $15 and $20 billion annually -- and growing! A report in New England Journal of Medicine back in January 1993 showed that about one-third of American adults had sought some sort of unorthodox therapy in the preceding year. It might seem reasonable to suppose that atheists are much like the general population in such matters, but it's hard not to hope that atheists are as skeptical towards alternative medicine claims as they tend to be towards theistic claims.
For some atheists, as with many theists, alternative medicine might serve as a replacement religion. Alternative medical treatments give an impression of being scientific and rationalized like regular medicine, but at the same time they promote a vision of the world which is holistic, supernatural, and altogether consistent with common religious premises (though contradictory towards rationalized science). It's not a "scientific" religion, but it combines enough features of both science and religion to serve some of the social and psychological functions of both.
So, in at least giving the impression of combining the "best" of both science and religion, alternative medicine ensures that it can attract a broad cross-section of America. This may not be the answer to why it is so popular, or why otherwise rational atheists might be attracted to it, but it is certainly an important ingredient. It's unlikely that these are factors which many customers of alternative medical practitioners consciously think about, but it's implausible that they don't play a role.