While the intention of the extension specification to OAuth2 for device codes is indeed intended for handling authorisation on devices where the user cannot use any input method on the device,
it's also very useful for when we want to authorise older devices where there are other difficulties, such as outdated or intentionally omitted root certificates making it only possible to use
plain HTTP, or just other sorts of applications where having to make a web UI just for receiving the authorisation code to complete the token request would be a bother,
for me such a case would be bots like Satori.
It essentially just replaces three-legged authorisation from OAuth 1.0a but without the needlessly complex annoying aspects of OAuth 1.0a.
Beyond that I'm also just sick of entering my ridiculously long, randomly generated password letter by letter on the inaccurate touch screen of the Nintendo 3DS.