To plug his last-gen (not current) laptop into the new screen. They only put DisplayPort on the new display which is ridiculous. It's literally only compatible with the new MacBook/Pro. You can get an adapter one way (DisplayPort -> DVI) but not the other (DVI -> DisplayPort).
The display is about 3x overpriced anyway, it's not like it will be a hot seller.
I was just noting why you would need the DVI-to-Mini DisplayPort connector. I don't have the newest MacBook or that display, but there was confusion as to why that adapter would come in handy.
I am not interested in the display, I'm happy with my Dell 24".