What...why? D= Too simple?
Essentially. It's mostly the lack of character on the blade, it doesn't have any apparent dimension or detail. Yes, the sword is a prop, but it's not as convincing a prop as everything else.
"There is a theory that states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened."
- Douglas Adams