I thought the same thing so I disabled the backlight on my laptop's keyboard. After accidentally turning it on in the dark a month later I will never go back to a non back-lit keyboard.
It's hard to place your hands on the keyboard in pitch black or when you're in a weird position like lying on your back with the laptop on your chest. If you've ever partially closed your laptop so that the monitor would shine on your keyboard so you could find 'f' and 'j', you know exactly what I'm talking about.
And also TFA says "for a true typing experience you need to see your hands, and we’ve created a way to use the Vive’s existing tracking to do that".
The way I know where to place my fingers on a dark keyboard is by feeling for some raised bumps which are on the f and j keys on my keyboard. As long as I've got those, I can always easily put my fingers in the default position on the home row, and from there it's easy.
As long as I can use such markers to position my hands in the proper initial position, I really don't like to have a lit keyboard in the dark. It's distracting and annoying.
If your keyboard doesn't have such bumps it's easy enough to make them either using some craft materials you can stick on the keyboard (like some tape even) or by cutting small notches in to it using a file or a dremel tool.
My dad had a keyboard with those bumps rubbed almost completely off. Occasionally I would need to use the computer attached to it and found it really hard to use. I'm so accustomed to unconsciously placing my fingers correctly using them that without them I was really ineffective with the computer and found it frustrating.
It's hard to place your hands on the keyboard in pitch black or when you're in a weird position like lying on your back with the laptop on your chest. If you've ever partially closed your laptop so that the monitor would shine on your keyboard so you could find 'f' and 'j', you know exactly what I'm talking about.
And also TFA says "for a true typing experience you need to see your hands, and we’ve created a way to use the Vive’s existing tracking to do that".