amok: I think there must be more to it than that. I have a feeling this can not be the only reason why we almost never see gOg keys in bundles. I think gOg generally just dont participate (for various reasons) in this practice. Also, it seems they do not have the same infrastructure on generating keys as Steam have, so it is not as easy.
Grargar: What would be more profitable for a company that deals in only one method of activation? Steam. Even if GOG keys were easier to generate, I doubt we'd see them in bundles from big companies.
For Indies? Maybe, but Disney is far from an Indie company (maybe an Indy company).
For a company, there is really no difference in Steam keys or gOg keys. All they need do is distribute the keys, and let the store deal with the rest. If the key generation process for Steam and gOg was equally easily accessible, there is no logical reason of preferring one over the other.