Is a conspiracy of bait and switch.
No-no-no-no. Why you can never get the advertised mileage after you bring the car home? How come your TV, when actually measured, is not quite the size they told you? How come a big Mac advertised as 2.99 and by the time you have to pay, is $3.50?
On HD, the excuse it, OVERHEAD. They are telling you, space are needed for the folders and managing components even without actual data. Like a house still occupy space with no people in it.
Bottom line is, nothing none of us can do, it is what it is.