This method prevents the user from trying to recover with a backed up encryption key, or booting live media. Instead it makes it clear that this motherboard is compromised and cannot be safely used.
If you care about this specific attack scenario then make sure you check the keys with a management tool or something. It's not necessary to make the chip unusable for almost every aftermarket user just to make it a little bit clearer that a compromise has happened in that rare case.
I'm just trying to speculate what might be driving demand for this type of feature, since TPMs already exist.