There was a theory, back before the subscription era, that the reason stolen/fake Photoshop license keys would work across multiple versions was that Adobe actually wanted people to be using pirated Photoshop at home. The people pirating Photoshop were theorised to turn into the same people who'd demand it at their workplaces, and Adobe was quite happy to go cash in on the corporate licensing. Easily piratable Photoshop was a free training program for future Adobe customers, who weren't going to pay for a copy to use at home, anyway.
Who knows if there's any truth to that, but it doesn't work in the subscription era, which definitely opens up some space for competition.