Why Have "Useless" Talents?

Every class has at least a few talents that are normally ignored by the vast majority of players. This can be for a combination of reasons; for example, the talent could be best suited for a build that focuses on, say, defense...but be deep in the offensive tree of that particular class. Or the talent could just have such a marginal effect, or be an improvement to an ability or spell that people hardly use anyways, that it has just about no desireability whatsoever. I suppose that these talents might be in there just for the oddball that doesn't want to be a cookie cutter, but other than that they just seem like a waste of space.

What I am wondering is why even have such talents in the first place? If nearly no one wants to use them, isn't it pointless to have them at all? I'd just like to get inside the developer's heads.

Anyways, for fun, why not post a few of these talents so that we can start some endless debate about how <insert random useless talent here> is actually not useless, or is indeed useless. I'll start with the Warlock and Shaman classes, the two classes I've played the most:

Shamans
Currently its hard to say that shamans have a useless talent, but in the BC we get a few. Elemental Sheilds would be one; this clearly defensive talent is too deep in our offensive tree. Another one that is borderline useless is Totemic Mastery...I say borderline because I can see non raiders and raiders who are beyond earthfury might want this. The effect is still pretty marginal though.

Warlocks
*Improved Enslave Demon: Basically, I hardly ever use Enslave Demon. There just aren't enough demons worth enslaving, and the effect tends to backfire at the wrong times. Not to mention that the vast majority of demonology talents improve the pets that you can permanently control, and casting this spell
removes all of those benefits.

*Improved Firestone: a talent that benefits your destruction tree...that is deep in the demonology tree. I guess that maybe you'll see a few strange people who want the best of both worlds but instead like to gimp themselves completely...but otherwise this talent serves no real purpose.