Paying monthly for software is a scam
Tl;dr: You did not own the software.
When you purchase a program on a CD, what you typically own is a physical copy of the software and a license to use the software. This license outlines what you can and cannot do with the software. Common rights granted include the ability to install and use the software on a computer, and possibly to make a backup copy for personal use. However, you do not own the software itself in the sense that you could redistribute copies, modify it, or use it in ways not permitted by the license.
This legal concept of software ownership has not fundamentally changed in the last 20 years, but the specifics of licensing agreements and the enforcement of digital rights management (DRM) have evolved. Two decades ago, software often came with "shrink-wrap" licenses, where the act of opening the software's packaging constituted agreement to the software license. Today, software licenses are more commonly agreed to digitally via click-through agreements during the installation process.
The shift towards digital distribution and cloud-based services has also introduced new licensing models, such as subscriptions, which grant access to software for a limited time, further emphasizing the distinction between owning a physical copy and owning the software itself.
In summary, owning a program on a CD grants you a license to use the software under specific conditions, not ownership of the software code or the right to do anything you want with it. This principle has remained consistent, though the details of how software is licensed, accessed, and used have evolved with technology and distribution methods.