I agree that no matter the build there is always at least one shout that is useful, but in some instances it just makes sense not to use them. Mostly it'd be for a build whose rp would prevent them from doing the main quest. Or for rpg purist that are used to playing without special powers. Personaly I think they should be entirely optional and you should be able to do the main quest without having to use them. That's why I usually always end up learning at least Unrelenting Force, Whirlwind Sprint, Clear Skies, Dragon Rend, and Summon Dragon as they are required by the main quest. Also other than required parts of the main quest I don't use them.