Why don't the 4 playable races have the same number of trainable units?

[CheeseEtc]

Excluding workers and heroes, humans and orcs have 11 trainable units, night elves have 10, scourge has only 9.

Same for buildings. Humans and Undead both have an extra building with no equivalent in other races (lumbermill and sacrificial pit).

Is there a balance/gameplay reason for this? I think this is relevant for custom races.

 

[Spacebuns]

Because each race has a unique identity

 

[Tryce09]

Are you counting the alternative forms of both druids + hippo rider? thats +3 units because druid beast form and hippo rider have other combat rol(heavy warrior tier3, flying support and advance flying unit)

The same for the undead (Obsidian destroyer, shade and the skeletal minions(2)