It seems that a lot of reviews of devices, be they ultrabooks or laptops or tablets or phone, often have a comment in the discussion about storage about "what is available to the user" Have you ever read a review where they mentioned that?
I'm not arguing that its "fine" that Microsoft only leaves 35% of a 64GB SSD to the user, I'm suggesting that you, Zirro, and perhaps lots of other people, will either look at a review or a description, seek out the available space number and pause and say "Hmm, I think I'll pass." (or if you really must have a Surface Pro, and you want about 64GB of space get the 128GB model, and gripe righteously about how bloated that seems relative to other situations.