This is just the default game as far as I know
You can download mods that change the loose loot spawn rate but I'm not sure if there are any that target keys specifically
It's one of those things in the game that BSG has ignored/nerfed over time and finding keys in raid in loose loot locations is so rare that you probably will never find them
If someone has a mod that targets key spawns that would be awesome but I don't know of it