[mamon]

I think that with graphic cards it is a little different: the manufacturing process is simply not perfect, so attempt to produce card with 56 Streaming Processors (Pascal) can result in 40 SP units working fine and 16 being broken. So you disable broken units and sell the piece as lower end card instead.

[tcoppi]

They also do it on cards that pass the higher-end binning process fine and sell them downmarket anyway when there is more demand there.