Because you are doing it wrong. It should be like this:
@using (Html.BeginForm("ComicAdder", "ManageComics", FormMethod.Post, new { enctype = "multipart/form-data", id = "addComicForm" }))
{
<div class="add-comic-submit">
<input type="submit" value="haha" name="haha" />
</div>
}