Emperors Want to Conquer

It makes sense that emperors want to conquer. Imagine that France had won and controlled the entire American continent in the French and Indian War, leaving England without colonies. The economic development which could have formed out of such a success could have elevated France to a position of sufficient power to expand in Europe, taking control of the other countries around them.
Going along the same lines, if England still controlled the American continent, it is not a far stretch to think that they may now control a much greater share of the known world through empirical expansion.
If England kept the colonies, France may have one day ceased to exist.
If France kept the colonies, England may have one day ceased to exist.
What kinds of incredible knowledge and culture would be lost if all the world were English?
Even if they are greedy blowhards, emperors and kings serve an important purpose when they expand their power and lands: they preserve their culture and belief systems from being destroyed by the other cultures and belief systems.
It is as if all of the empires of the world check and balance each other with war to keep their ideas alive. I'm not a proponent of war or conquest, (in fact, all of the good things about war would be accomplished just as well if nobody ever went to war because nobody would attack and destroy other people and their beliefs) but I see now how it benefits society, culture, and human knowledge.
It makes sense that emperors conquer.