This isn't unique to games, and it's not just "today". Go back a decade [0] find people making similar observations about one of the largest tech companies on the planet.
But it's stored because it's possible, easy, and cheap. Unlike older games, where developers would hide unused blocks of empty data for some last-minute emergency cramming if they needed it.
This reminds me of the old days when I check who's using my PC memory every now and then.