Well, what a lovely accusation, as well as a default condemnation of thousands of parents. Good call.
To OP: This is nothing new. This same thing was going on 30 years ago. This is often the time when children separate from their parents and try to find their identity and establish their beliefs as their own. They may also be exposed to, or pressured to, engage in sinful activities. Without an established church family and friends in the new area (as many times this happens to young adults going away for school) they lack guidance and accountability as well as having a new set of temptations, they tend give in eventually.
They are also hearing all sorts of new arguments against their faith from both professors as well as other students and may know how to handle a plethora of new assaults on their faith. These are, often times, the most common reasons.