> Nothing is stopping people from keeping an archived copy until copyright expires.

Which people? In the case of abandonware, the original software is often not in the hands of the copyright holder anymore, due to neglect or lack of interest. Sometimes all or most relevant physical copies have become damaged. All that remains is a (cracked) file download in an abandonware website. Thanks to the abandonware community it gets preserved.

Besides, a piece of software history only serves its purpose if you can experience it. With no way of legally experiencing it (you cannot buy it) how do you propose to experience it? You cannot always wait it out, you might die first due to how long copyright lasts. Or is this nebulous concept of copyright more important than human experience?