If you have access to, or are around a cutting torch some time, take a piece of round stock, say 1/2" or so, and clamp one end to a welding table. Hold the other end loosely in your hand, and just "wave" the torch over a spot on the rod. It will move far more than you expect.
Now picture a rifle barrel, that is not absolutely uniform, (they never are), that will have "hot spots" in it when shot. When you shoot that rifle, it will move ever so slightly as it heats up. Sometimes you can correct this with floating, sometimes with bedding, and sometimes not at all.
Most rifles we buy off the rack are hunting guns, and are very suitable for such as is. If you want 1/4" moa accuracy, you will have to either get very lucky, or work at it a bit.
Of all the rifles I've bought off the rack that were most accurate, I would list #1 my Savage Axis, #2 my Handi Sportster in 17hmr, and #3 my Handi 45-70. All I've done to either is some trigger work. All are sub moa, and plenty good for my kind of hunting.
Ben