I mean there's a very easy and obvious answer here. It's a paraphilia of its own. It's like asking why some weirdos are attracted to dragons fucking cars or other weird shit like that. We don't really know why people develop paraphilias, but most research seems to indicate childhood or adolescent experiences play a roll. That's not to say that the people who like that stuff aren't pedos, I really have no idea. But the concept is well established.

I have personally never been aroused by a drawing of any type though. Whether it's weird pseudo-children/teenagers in anime, or adult cartoon stuff. It just does absolutely nothing for me for whatever reason.