I actually don’t know how many programs do this, but several check that file permissions are correct or refuse to work. Sudo and ash are 2 of them. I could see /etc/shadow being readable and writable by everyone being a problem too, but I don’t know.
Yeah, they’re mostly bits of hardware that turn ttl/serial into a USB device. Then you can use minicom or dterm to connect to the host. Mostly used for embedded development, but also useful for debugging servers that are not connecting to the network without having to lug a keyboard and screen.
After they’re connected, if they speak vt110, your terminal emulator can display everything properly