Considering many collectors keep all of their purchases sealed, all they need is a nice slip. There could be just plain cardboard inside the slip, but why would that matter if you only see the shiny packaging? Haha
Or, you know, the slip has the title on it? My main gripe with titleless steelbooks is that it looks absolutely ridiculous on my shelf. When I ask my girlfriend to grab The Good Dinosaur from my shelf do I ask her to grab that movie or say "just look for the stupid case that looks like a dinosaur movie with no title on it"?