Why do I get a miniature of a beast instead of a beast itself?

Like, taiming King Krush should give you a giant Raptor that follows you, and that should be the main point of wanting to tame an Epic Large creature.

But instead, it gives you a miniature of it, which can grow with its level but will never actually be the size of the King Krush you found in the wild.

I never understood why.

The most they would ever be able to do would be blocking the mailboxes in Orgrimmar.

Having big creatures is fun.