Ignorance, and misunderstanding of what it is seem to be big factors for me.
Before I used to suffer, I never even used to bat an eye about what it was, why it existed etc. I didn't have a care in the world for my skin. That was 5 years ago, and ever since, I just can't help but look at every single person's skin and compare it with mine, be it better or worse.
Also I think the people who don't suffer and see people with problems on their face just don't understand why they have them. I assume they just instantly think 'eww look at how bad his skin is, he must be really unhygienic bla bla bla'. And this is the reason it gets me down so much. The amount of times i've been asked what have i done to my face, or what's wrong with it. I just sort of ignore the comment, or mumble something. But every time I just want to shout' I have no fucking idea!! I didn't do anything, it's just my fucking shit skin, now fuck off!!'..or words to that effect,