
I did a little more serious research and it turns out that 30 years is not that long for the law protecting the video games.
"For the most part, games published in the United States are copyrighted for 95 years from publication. This means that the first commercial non-arcade video games will enter the public domain in the US on January 1, 2073, when copyright on the early Atari 2600 games expires."
We have a long way to go...

Of course, the question remains why bother doing more new things when you can make money from work that was done 10-20-30 and even 40 years ago. I know that collections with emulated games are still the work of programmers, Nintendo's mini consoles also cost money to produce... But with them you know what you're paying for. You pay for the collection and the ability to play them on specific hardware. You pay for the hardware in the NES mini console. No one pays specifically for roms and no one ever buys only roms. I just don't see how letting the roms circulate freely on the net is going to reduce sales of the collections for new platforms or dedicated mini consoles.
But they own the games, they own the rights... they can do whatever they want with them after all.