Consider the following, hypothetical, two-part possibility:
Your advisor owed this guy a favor, so he brought him in and got his name on your paper.
AND
All the other responses here still have good advice about how to deal with it or put it in perspective. Even though they don't really seem to be admitting this completely plausible explanation.
I'm just saying this because some otherwise good answers seem to be going as far as attacking you, directly or by implication, for your attitude or reaction. But your reaction is completely reasonable, in the hypothetical situation I described above. And none of the people answering this know if that is the situation, or not. (And neither do you, unless the advisor specifically admitted this to you.)
And it doesn't even have to have been that egregious, the intentions may have been more pure. For example:
- your advisor really thought this person would make a significant contribution, but, when they turned out not to, it would have been extremely awkward to not list them
- you are bad at writing things up, it would be awkward to try to tell you this at this point, and your advisor knew that this person could help you with that, and brought them in for that reason, and you still haven't realized the value of that contribution
- your advisor felt that you needed to learn how to work with someone else on a publication, because you have a strong individualist streak and your advisor thought it would be good for you to learn how to put together a paper that is a group effort
All I'm saying is that it's completely possible that you're right, that this person really doesn't deserve to have their name on your paper. But I still think that the various contributions here might have some value for you, even though some aspects of them might come across as being unwarrantedly adversarial to you.
Read through the links in the "related" section on this page for an answer to your actual question:
is it normal to have people with little contribution be listed as co-authors?
I have to think that it's pretty common, just from people's stories on here. Academia is a human endeavor, and humans, in basically every context, are going to do human things, like quid pro quo and pity credits and so on.
Even if my worst-case hypothetical proposition above is true, it is also true that you can't change centuries of academic culture or millennia of human evolution on your own.
- stewing over this is going to be bad for you both psychologically and mentally, so I would strongly advise against it
- in order to not feel like this bad thing happened and you are completely helpless to correct the injustice, focus on the fact that, over time, you will be in a position to have more influence over the process, and you will be able to prevent something like this from happening to someone else who is early in their career and at a similarly low level of influence
- again let me advise you to consider that some of the advice in the other answers is actually potentially of very significant value to you in your career, so try to compartmentalize their apparent or actual dismissal of your concerns and just focus on the true part of what they are saying