There 3 main approach of that.
First one is from lazy ppl. They just recreate popular anime trop "make MC pathetic so he don`t drew attention" and concenrate on girls. And they prefer not to think about the fact that the game works a little differently than animation.
Second comes from inexperienced writers. They think`s that pathetic characters evokes sympathy. Like in Harry Potter. Also, they prefer not to think about disgust and other bad feelings that can come with contact with this.
And third ones just don`t like MC. And making him looks bad making them feels good.