Yep, this is the same as all the other Bethesda Softworks titles from the past few years, and every other PC game out there that uses Steamworks.
The reason to buy the retail copy would be if you want to have a physical box to put on your shelf, or if you have limited internet, as I imagine it will reduce the download time a bit because some of the files are already included on the disc.
In my case, I don't own any optical drive, so the only way I can install retail games is by redeeming the Steam keys. From my perspective, it would be the same if retailers just sold little scratch cards with the code for the game.