As an example, I'll reference scientists in Jetpack Joyride.
I do understand there are achievements that involve scientists, that you can kill them or you have a nerd repellent, but I am not asking about any of those.
I want to understand whether there is any very important reason to have such an element in a game, since (at least initially) it seems quite insignificant.
More precisely, does the presence of scientists (or any equivalent, apparently insignificant "actor" in a game) has any psychological effect or influence of any kind to the players? Or they are simply there as a small little feature of the game that barely makes any difference to the player's feelings & attitude whilst playing the game?