Just a continual exposure to the Infernal. First of all, since Hierarchy does not measure enlightenment, a mage who gives up the path of evil will find that they have spent years, possibly even decades, neglecting the search for Ascension. Many mages, realizing this fact, return disheartened to the infernal. At least that way they have some power. Secondly, there is the addictive quality of Hierarchy.
Failure means they jump right in.
Thus, as the mage falls deeper under the influence of the powers of hell, she finds it harder and harder to escape. As the mage continues to use Hierarchy, the infernal paradigm begins to subtly infect his surroundings. Neighborhoods get meaner, pollution gets worse, etc. To raise Hierarchy, the mage must spend current rating x 8. The storyteller, of course, can add to this list as he sees fit.