How about just... you know... backing up important data like license numbers?
Serials were the least problematic thing regarding physical PC games.
Non-standard optical discs trying to prevent backing up, rancid DRM drivers making Windows randomly go bluescreen and slow startup times due to disc verification and .exe decryption.
It isn't a matter of physical vs. digital as much as it is about Digital Restrictions Management. Companies have been revoking/restricting access to physical games for the longest time, too.
Discs will deteriorate earlier, but since most people don't store all their digital games and physical game backups, they're still the best choice for those who don't want to go the extra mile.
"Discs will deteriorate earlier"
I have to file this under myth. With literally thousands of pressed CDs/DVDs/BDs (audio, video, software, PC games, console games) in my collection and not a single one failed in decades I find the omnipresent fear of "disc rot" a bit exaggerated.
Under good storage conditions the discs are probably gonna last longer than I myself will (okay, the latter won't be very long)