I suspect a lot of these factory guns are either tested out of the stock in a solid mount, or not tested at all. If you are Springfield armory and you make thousands of rifles, are you really going to proof test all of them at $60 a box for ammo? Most guys can't shoot 0.75" groups anyway so even if the rifle ends up being 1.5" 90% of customers won't know, of the 10% that do, most will just dump the rifle, the few that send it in, still money ahead of testing every rifle with possibly multiple 5 shot groups. If 75% of your guns shoot to the guarantee, and 90% of the shooters can't shoot 3/4" groups, you aren't getting many returned.
I remember trying to get a Kimber Montana to shoot I bought my father when he retired ~2007, at that time Kimber's testing was removing the gun from the stock and shooting at something like 47 yards and extrapolating to 100 yards and their acceptable group at 45 yards was 0.75". Ended up trading it for a Nosler M48 ~2009, it also had issues, no pilars, did not shoot to the guarantee. Sent it in, they couldn't get it to shoot either, they rebarreled and modified the stock and returned it, shot okay. Ended up getting a Weatherby Vanguard Sub-MOA not long after, slightly heavier but shot much better than either even with the super flexy factory stock. All were 270WSM.
I bought an HS Precision PHL 300 win mag for an elk hunt back in 2010, came with a tiny test target probably 1/4 MOA. Wouldn't shoot 1.5", even with the load they tested it with, sent it to HS, they couldn't get it to shoot either and were "baffled" took them months to rebarrel it. Again when it returned it shot okay, but no where near that first test target, even for them with the new barrel and a hand load.
Sometimes it goes the other way, I have a bone stock Rem LTR .308 that just hammers with FGMM match ammo, better than I can shoot it, don't think it was even $900 at the time. My first deer rifle was a browning A-bolt in 30-06 from the late 80's, for a factory $500 deer rifle it shot amazing.
You have to ask yourself how does this happen to new rifles with accuracy guarantees, some of which are north of $3k? I see only 2 ways, either they aren't testing them in the stocks as they ship (which is my guess for many that include test targets) or they aren't testing them at all (or only spot testing) and just accepting that X number will be returned. The only other option is they are somehow damaged in shipping or at the gun-store, to the point it's destroyed the accuracy of the gun, that seems pretty unlikely.
That said I still think companies should pay me to buy their products to get lemons off the market, I seem to attract the worst QC examples of even the most bulletproof products.