They might just be proud of the results they are getting, I used to train a male who was quiet overweight when we started, his wife had left him with nothing while he was at work one day (came home to an empty house....completely empty). Anyway, he lost all his weight and looked pretty decent but it was hard to get him to keep his shirt on..... I guess he had to keep checking that he was actually as lean as he thought he was. I think there is nothing wrong with it if it motivates you and you are not conceded by it....... and you are not doing it in front of people you may offend, lol.
Also, you have to practice posing if you are competing cause you can sure tell who hasn't when they get on stage.
As far as gross stuff in locker rooms goes posing is pretty tame!!
We had to take down the shower curtains in the mens locker rooms due to the things happening behind them