
Originally Posted by
Mr Prophet
They aren't heirs so much as underlords. If all the 'children' carried in the Jaffa were allowed to take a host, they could have taken everyone in that cell and still needed a few more raids; the Goa'uld chose to retain a certain number of children as sub-commanders. Even then, their children are the biggest threat to their power (Children of the Gods), but I guess it's a choice between that or trusting a stranger or a mortal to govern part of your realm.
But basically, there's no mileage in the spread of the species, as far as the Goa'uld are concerned. Sooner or later - and probably sooner - there would be far more Goa'uld than the galaxy could support; why not take them out when they're small and helpless.