The folder System32 was never updated to System64 because of the many apps indexing to the folder System32, and they would have all broken. Some of you smart people will have noticed however that there are different software versions for 64-bit and 32-bit: why then not make the 64 bit version of a software index to System64? The reason is backwards compatibility, or the ability to run outdated programs on a more recent architecture 32-bit software can run on a 64 bit machine thanks to the System32 folder not having had any name change.