You have to remember that these games were made a long time ago, before the popular professional gaming events even existed. 30-40 does seem a bit low, but I doubt they had any conception of the actual upper threshold (300+).
Also, AOE is much different than Starcraft/Warcraft. There is much less microing involved.
Agree. I recently reinstalled AoE on my machine (my gaming never really evolved past 1998), and I can truly spend 2 minutes without issuing a single directive.
In a 90 minute game, the first 15 minutes might involve very little instruction at all - quite different to more modern expectations of game play.
Check out Rise of Nations (gaming circa 2003): it took the Age of Empires style to its logical conclusion by crossing it with Civilization, and it includes lots and lots of features to minimize micromanagement. Things like idle workers automatically finding a nearby resource node to work.
Also, AOE is much different than Starcraft/Warcraft. There is much less microing involved.