It happens because we know the engine is limited to a certain amount of people (The Culling), and then your own teammates have been in the field for longer so they are all drawn up and you can see them.
What if the engine decided, that at a certain density of teammates, it would draw half of them or something. If they could do such a thing to avoid you seeing all of yours and none of the enemies, that would really help.
Instead the green dots on the map would tell you exactly how many you were, and the engine would be ready to draw up some enemies when they entered the field.