try to backup nwn2 and play with it. you can't. so does in most games.
Yes, you can
. If you can't do it yourself, then all you need to do is download an image of the CD or DVD via your favorite torrent client. Actually, this is exactly what Steam is, too. At the core of it, it's just another torrent client. The difference to other torrent clients is that Steam has a shopping/billing system built into it and it's also got an auto-patcher tagged on. That's all there is to it, really. Nothing more, nothing less.
I have nothing against Steam but so far I have with one exception (when my DVD drive couldn't read the HL2 DVD which was actually not the fault of my drive but my bad/incompatible memory but I'll spare you the details
) not seen a use for it personally.
I think it's great for people who live in countries (like Australia, NZ, entire APAC region etc) where games often get released months after the US/European launch but as an American or European gamer, there's mighty little need for Steam IMHO. For example, Vampire 2: Bloodlines can be bought from German online retailers for half the price of the Steam version (~EUR 10). Every single other Steam release has so far been more expensive than the game at retail, too.
The only two advantages of Steam that I can see are that you don't need to get out of your chair to buy a game (which can be advantageous if you live in remote areas) and the built-in no-CD/DVD "crack" (DRM)... which is not quite exclusive to Steam though as cracks exist for most retail games as well. The difference is that with Steam you have a guarantee that the game will always work with no CD/DVD whereas you need to rely on the various release groups to care enough to hack up a new crack for a game when a patch is released which does not always happen.
On the other hand, you have retail games like Oblivion with no protection that work with just the image on your HD so it wouldn't be quite correct to claim that Steam has a general, overall advantage in this area.
So in summary, I see the biggest advantage of Steam in its ability to bring the Steam games to more people, i.e. those people who do not get timely retail releases or maybe even no retail releases at all.