While there is truth to the theory, it's not like the SNES was backwards compatible with the NES.
Nor was the N64 or Saturn BC with their very successful predecessors.

The PS3 wasn't really BC with the massively successful PS2 either, apart from the initial run of NTSC consoles.
By the time the PS3 hit PAL regions, they had already stripped out the EE and it was depending on sketchy emulation which itself was completely scrapped by the time the Slim came along.

But I'm speaking from the point of view of someone who hasn't sold on a console since the SNES.
While I did sell my Mega-Drive, Mega-CD and Saturn at various points, I was able to reacquire both of them.
And I mean reacquire the specific units! :)
The SNES was the only one I sold to an actual store (in order to buy 3 additional N64 controllers for Mario Kart 64).

Both the PS3 and the Wii ultimately removed BC in later models.

: Uh, no. A lot (maybe not the majority, but a LOT) of PC games do not
: require/have not required an access code in the past. Also, very, very,
: VERY few CONSOLE games have in the past.

But Games for Windows Live do.
Even if you buy via Steam, you are provided with a key code that locks the game to your XBL account.
Actually, this whole system for the Xbox One seems to be based around GFWL.