Quite simply, because "society" doesn't understand it. Generally speaking, people only care about things they've been forced to understand through personal experience. And, to be honest, I think this site is a great example of this -- people often use their own experience with acne as a basis for their overall opinion about it. They're quick to demean acne by either comparing it to more "serious" conditions or by offering simple means of treating it. Around here you may not hear things like "you need to wash your face more often," but the same sentiment is shared (in more indirect ways) quite often.
Is this "wrong"?
Perhaps -- but, at the same time, I don't think it's fair to declare people as being "too dumb nowadays." It's very difficult to understand something you've never experienced; and, for a majority of "society," acne is nothing more than a very treatable -- and temporary -- nuisance.