Sure they do: stock assets are the most obvious market that AI is taking direct aim at in games development, and the AI tools on the game dev market were largely trained on stock assets. If you need anything from a sound library to a 3D model to an animation to an icon set to background music to network gameplay code… sure you can get it through stock asset marketplaces… but AI tool vendors have ingested many of these stock assets and hope game developers will buy their tools to generate assets rather than buying the stock assets they built their tools with.
Code libraries and your house do not fall in the category of "things that give you game assets without you having to make them" because they do not give you game assets without you having to make them. (Code is not considered a game asset.)
Asset packages are in the category of "things that give you game assets without you having to make them", because they give you game assets without you having to make them. The assets in the package are, by definition, stock assets.
