Definitely don’t this in the past (Linksys WRT54G!) but let’s be honest, the kind of people running 10yo Dlink routers aren’t going to flash new firmware, let alone OpenWRT or even know to look for it. It would have to come that way from the factory. And even then I doubt most people even do regular updates, sadly.
It’s because you need a cloud based account for a local device that should be able to run without internet access using a local only account. I don’t need a cloud based account to log into my local Linux machine… or previous Windows machines.
Now, if I want to log into a cloud service then I’ll need an account for that service, but not for the device itself.