Sure there is; what do you think the login is for?
That was the case prior to the DMCA. Then it added a provision making it illegal to circumvent copy protection mechanisms. That is why copy restricted formats like the ones Apple uses to distribute music are so insidious. You may have bought the song, and you may have a copy of the file on your computer, but the moment Apple decides, for whatever reason, not to authenticate you to play it, you are screwed because it’s illegal to break the copy protection on it, even though you own it and are just doing so in order to listen to it.
It’s been probably 2 decades since I studied it so I may have forgotten, but I feel like that was not an exception granted. Either way, how many people are going to figure out how to crack it themselves? Not many.
I agree that it is important, and that is exactly why the DMCA is evil: it does make it illegal for you to circumvent the copy protection on that DVD that you own, even if it is only to play it on your Linux computer, which the powers that be have not authorized to be a valid player.