The manufacturing process for semiconductors uses a standardized wafer size (in a given fab) so everything can be automated and simplified as far as possible. H

The manufacturing process for semiconductors uses a standardized wafer size (in a given fab) so everything can be automated and simplified as far as possible. Having even something like just two wafer sizes makes a lot of the tooling/storage/transfer more complicated and expensive, so it's best to stick to one size and shape. In order to have uniform rectangular slices of the silicon crystal, you'd have to slice off horizontal cylinder segments. And that would defeat the purpose because if you just used circular wafers you'd have been able to get a couple dies out of that area.