There's a valid point to the OP's request which many seem to be overlooking - boxed copies provide tangible extras like a manual you can read while playing the game, rather than a PDF you have to continually Alt-Tab to view.
Unfortunately, as Raze has noted, Larian made their physical version reliant on Steam though they later agreed to provide
DRM-free DVDs to Kickstarter backers. It should be possible to extend this courtesy to retail purchasers too (and if physical copies have been sold out, to produce a new batch with Steam-free discs) but anyone interested would need to contact Larian support to ask for them.
