[IronJack]

There is little doubt that guns, bows, knives, and automobiles are penis extensions (for the Freudian-inclined). There's also little doubt that that is perfectly acceptable, since they are merely projections of male sexuality. They are only "wrong" if male sexuality is wrong.

Oops! I think I may have hit on the core of this theory ...

[SmoothTalker]

"There is little doubt that guns, bows, knives, and automobiles are penis extensions (for the Freudian-inclined). There's also little doubt that that is perfectly acceptable, since they are merely projections of male sexuality. They are only "wrong" if male sexuality is wrong.
"

They are shaped this way for the simple reason that this shape works well for a weapon. A vagina isn't a shape you can kill with.