Ever notice how every pretty much precursor race in science fiction leaves the following crap behind:
-Sealed evil in a can
-Weapon to defeat said evil
-Horrifically dangerous experiments
-Galaxy-killing weapons
-Some sort of "passing of the torch" to humanity
It's always sort of "why didn't they use the friggin anti-bad guy gun when they had the chance?"
Well, the super advanced civ is usually portrayed as being too stuck in their mindset to be able to think differently. For example, the Asgard were certainly advanced enough to defeat the Replicators but they admit to SG1 in that episode that it would never occur to them to build gunpowder based guns like what SG1 uses. O'Neill comments that the Asgard need someone "dumber than them".
And, we see in Ark of Truth that the Ancients were unwilling to use the Ark for ethical reasons but SG1 was willing to use it.