In CPUs, there's at least a legitimate reason: reducing wastage by, e.g., selling what was intended to be a quad-core but had two defective cores as a dual-core instead of throwing it away.
That's only partially true though. Back in the day you could "unlock" cores in some AMD CPUs, which indicated that they were perfectly functional. Nowadays they disable the cores in a more robust way, but I doubt every disabled core is non-functional.