Wherever there is room for completing a goal within a game you enjoy playing, it makes sense to have accomplishments. If this wasn't the case, people wouldn't play.
I understand what you're saying in the stance that people shouldn't feel as proud as they do about it all because it's something so minor to care about but you must surely understand the concept of it.
Say that to eSports companies/teams and streamers who earn more than 5x what both your parents earn per annum. Granted, your post was aimed not particularly at these people but to say games accomplish nothing is ridiculous and narrowminded.