There is smaler, taller, thicker, ... bodies. In general lot of games using same hight or silhouette of playable characters. There is only difference between faces or other things like that.
Example of different hight in Multyplayer games:
Stay and look around, in 200 metres there is silhoutte of standard size of playable character. Easy target for rifle you think, distance is quite suitable, you try to shoot and all is OK. But what about smaller silhoutte, same distance from you only smaler size of character. You know that its 300 metres but it looks like 300 metres away. But if you dont know you try to shoot him, but you miss him due to wrong distance calculated in your mind.
....
Example of different hight in Multyplayer games:
Stay and look around, in 200 metres there is silhoutte of standard size of playable character. Easy target for rifle you think, distance is quite suitable, you try to shoot and all is OK. But what about smaller silhoutte, same distance from you only smaler size of character. You know that its 300 metres but it looks like 300 metres away. But if you dont know you try to shoot him, but you miss him due to wrong distance calculated in your mind.
....