Earlier quoted context omitted.
Public domain does not mean public. The source code could remain a trade secret. More of an obstacle is competition from free past versions - a lot of people would be happy with a 10 year old version of Photoshop or MS Office. That's why I think it should be extendable to 20 years with a hefty fee (but not further, or only with a much heftier fee).
If you do not publish source code, your binaries should be ineligible for copyright protection. There is very little creative work in the binaries themselves. Keeping your actual creative work hidden (especially from things like eventually being part of the public domain) but yet still expecting to receive the privilege of copyright is inequitable. Same thing with only publishing under digital restrictions management…
The GPL defines the source as the preferable working format to make changes and updates to the program, but you can see how that definition blows up in your face when there is no published source to begin with. "Your honor, that 50MB binary file that has a signature of a GCC compiled program IS the preferred working format for our company; indeed, it was created from temporary text files, but they were deleted as they were deemed unnecessary for a technically advanced company such ourselves. All further updates will be made in assembly language via binary patching, for maximum efficiency".