why does rick and his crew always ask people they meet. how many walkers they killed?

they want to know if they can defend themselves

Because he needs to know how these people survive and how scared they are. Like if it is three years into the apocalypse and they say that they have been roughing it and haven't stayed at a camp and have only killed 20 walkers it is obvious that they are lying!! It is important but at the same time not...