Because they wrote the code for determining your children's stats as a broad range....and left it at that for the time being.

I always marry an adventurer or royalty if possible, also not just adventurer trait but +1 added ability like vengeance.. Royalty is just for added prestige to growing cities, which seems only to work for units with essence.

I was marrying people distinctly different in appearance to my sov in an effort to see how their offspring would look.  You can get some "interesting" results.    That probably isn't the most sound strategy now that I see what kind of stats I could be getting.  

Ok so.. I ran into one of those super monsters.. this thing has some 20k attak, 13k def, some 1100 hps.. I was one of those rock spider things  cant remember the name of.. Had teleport, and a friend just as mee but somehow was at 14 hp of like 1200..

So I take myself my wife my uber son and a champion, and attacked this thing with 7 young dragons, and used the infinite range true dmg attack, doing 40 a hit. After the fight My Sov and friends gained something on the order of 65 levels, and some 165k in gildar...

*LOL* Sounds like my first game of Bard's Tale 3, in which - after I met and killed the first boss monster - my ressurected wiz was a full blown archmage all of the sudden.