I see the attachment feature as a convenience to attach small files, including images, for those who do not have an image server to link to. I think this is the feature the OP had problems with using. From what I understand, this is the intended usage of the "attachment" feature. I have seen nothing to suggest this to be a "back door" use. Why would you think that? I think a user would have to be pretty persistent in order to abuse this feature, considering the 4 attachments/post limit and the limited upload speed.
Its not a photo gallery, and does not function like one, just a simple way to add a few small photos, text documents, etc. Stuff you want to appear in a footer below your post.
The size limitations make it difficult to view.
You can argue over terms all day long, I call it a back door because its not the normal way people show their images.
You can currently attach the following: