Yeah, you need a much smaller number for e.g. giving access to journalists/media pre-release. But the key mechanism is also used for any legitimate sales or giveaways that happen outside the Steam platform.

If you buy a Humble Bundle, you get a set of Steam keys for the games in the bundle. If Intel/AMD/Nvidia are doing a promotion for a free game with a purchase of their product, they give you Steam keys. Etc.