Why did EULAs for purchaseable, installable software become the norm?

Question

I understand that web services need Terms of Service in order to regulate what goes on "under their own roof". However, why did EULAs become a thing for boxed, purchaseable software that was able to just be installed on the owner's PC?As far as I understand it, copyright law already had everything these publishers needed in order to stop piracy. For example, why even have a clause for disallowing reverse engineering, if redistributing a cracked version already counts as a "derivative work", and thus copyright infringment?

tlb · Accepted Answer

They were trying to stop pirates using a workaround to avoid copying. Instead of distributing cracked versions of the software, pirates would just distribute cracks -- tiny programs which would edit the binaries of software to remove the copy protection mechanisms.While cracks are still made and distributed by amateurs, they can't be developed at large scale by commercial companies because of the EULAs.