this feels like a missed opportunity , like they could have used that gold to buy a never-ending supply of slaves or hell just released it to the global market to crash the price of gold to cause as much chaos and economic ruin as possible and then capitalized on the resulting instability
This is a 'But I don't WANT to cure cancer moment', my man.
A: Horned Rat, with all your incredible powers as a God, powered by the faith and acts of devotion from a populace of billions, you could do so much! You have the numbers, the powers, the strength, the advanced technologies, the mutants, and the resources beneath the realms of men across the Old World! You could kill them all with great speed and efficiency! You could ruin them even with devaluing gold massively by pushing your vast riches into their coffers and ruin their economies!
HR: But I don't WANT to do it with great speed and efficiency or that stupid economy thing! I want my people to be nasty little treacherous monstrous cannibalizing fearful smug murderous exploitative treacherous gribbly monsters that deface, defile, destroy, denigrate everything around them, including each other!
That is what a skaven is meant to be, because I'M the one that made them!
A skaven leader might try and futz around with gold and stuff like that, but...that would mean putting gold in the hands of no-furs, and that's no fun. Besides, what if they get too strong and powerful by doing it, and their rivals get in danger? No, no, much safer to kill the skaven talking about all that business, it's only right, what if they conquered and won accolades and warp-tokens by doing it?
^and so it goes.