Why aren't cartoon animals anatomically correct?

This is probably an odd question, but one that has puzzled me for years. Scooby Doo is male, but you can only tell that by his voice and mannerisms. The same goes for Marmaduke, and other popular cartoon animals. Is there a particular reason as to why anthropomorphized cartoon characters don’t have physical sexual characteristics? Is it because no one wants to focus on the fact that cartoon characters, if they are alive, must have bodily functions?

The procreation of cartoon characters is a subtle subject in these animated shows, in that Donald Duck has nephews, but no one mentions how they were conceived. That is just one example, and I am sure there are plenty more, but maybe someone could help me figure this out.

Or perhaps I am just a pervert who looks at everything with erotic colored glasses?