This mostly concerns RPGs, as generally they are very easy to beat and even the extras are not too difficult provided sufficient leveling.
Speaking of which, I find too many people I know max everything out in a game and then just fly through it, and then complain about it being easy or just not have the initiative to play it again because they already "did everything". Whatever happened to just playing a game and enjoying the story or something? To those who do this kind of thing, is there some kind of special allure to completely beating a game only to never play it again?
I kinda used to do this for a while with some of the FFs (when I had a project to write walkthroughs and list FAQs for all the games), and I just stopped after a while because it became a chore for me rather than a pleasure to play the game.