When I first started my warlock, (who, by the way, was also my very first character,) shadow bolt seemed to be the thing. It was solid burst damage that took people out pretty fast. It was also the attack with the least confusing application. As such, when I recieved my first precious talent point at level ten, the choice seemed obvious. Why improve my hit chance with affliction spells, or lower the casting time of corruption? Why improve my imp, or my healthstone, or my stamina, when I could shorten the casting time of my shadow bolt? It is, after all, the mainstay of how I play!
As levels went on, destruction continued to draw my points. Double crit damage? heck yeah. An instant cast direct damage spell that gives me a soul shard? who could say no! It was right around the time that I was greatly enjoying the benefits of 'Backlash' in Un'Goro crater, shortly after I started
At the same time, a friend of mine with a level 70 warlock was continuing to insist that I should spec affliction. I don't like to give in to the insistance of friends for no reason, but this particular friend has the uncanny ability to be completely unreasonable, yet still be right about things. And, since I was dying constantly, I decided to take his advice and spec affliction. I wouldn't say that I absolutely loved it, there are many things that I missed--and still miss--about destruction. However, with a whole new set of skills and abilities unlocked for me, I gained a new appreciation for the depth of the class, and the pleasure I could have playing it. Save for a few brief stints respeccing to destruction or demonology just for the fun of it, I've been affliction ever since.
There's still a part of me, though, that really thinks of myself as a destruction warlock. A part of me who holds on to shadow bolt as the core of my damage-dealing ability. And while I have much less of a connection to demonology--I don't actually know my fel guard's name--I do have fond memories of the amazing things I've been able to do back when I had points in Improved Voidwalker. You might say that, in spirit, I'm a 72/73/73 warlock.
However, in body, I'm spec'd 56/0/15, because I'm good at it. I started spec'ing this way because I was told it did the best damage and I wanted to do the best damage. I stayed spec'd this way because I've since become very familiar with the proceses involved in optimizing this spec for good DPS. If, someday, some other tree, either demonology or destruction, is the clear leader in DPS. Then I'll switch. It would have to be a rather large gap, I think, for me to so readily give up the expertise I have with affliction, but I would relish the chance to play with a different aspect of my whole. As you might imagine--I can't wait for dual specs to open still more of the class up to me.
And there it is. I spec affliction because it does good damage, and because I'm good at it. I have no compulsion to cast dots, no passionate love for this particular placement of talent points. Not because I don't love the intricacies of playing affliction--but rather because I love the intricacies to be found in each of the three specs.
P.S. (First person to notice the pun in the post title gets a cookie.)