It's marketing lies allowed to become reality.
You buy a HDD advertised as 4Tb, plug it in, & the "formatted space may be less". Ok, then how can it be used *unformatted* such that it actualy makes available all the space it was advertised as having? If I have to format it to use it & no known OS has a file system that will leave the drive in a useable state with the advertised space, then how is that not false advertising? If you say it has X but nobody can ever use more than X-Y of it, then there is no ethical, moral, reasonable, or legal way you can say it's got X.
Ditto with screens. Nobody measured things diagonally when it came to describing their size. If you needed a cabinet that was 100CM tall, 100CM wide, & 100CM deep you went looking for a cabinet with those dimensions. Then the screen makers pulled the diagonal measuring method out of their asses so they could sell a smaller screen described at a larger size. The aforementioned cabinet will easily hold a "100CM" screen because the "100CM" screen is actually only ~74x74CM "but has a 100CM diagonal!" BFD. Putting it in that cabinet proves it's *not* a true 100CM screen.
Or they festoon the description with so many caveats that it's essentially impossible to get what you think you're paying for. The precooked weight may be as advertised, but the act of cooking it so it can be eaten means it's now severly less. The power output may claim to be one thing, but that's only if you do X, Y, & Z in a controlled environment "because conditions may vary" & thus bring down those values. Blah blah blah.
It's all marketing bullshit allowed to become reality. I wish it were legal to smile at the lying bastards & then strangle them to death with their own forked tongues. It might not solve the problem, but it would certainly make me feel better.