SoE, like any company, tries to make money for its ownership. While people complain that SoE is ALL about the money, nearly everyone on this planet of ours is about the money. I know that I would certainly not work for free, and I don't expect Sony to, either.
Now that is out of the way---Most of SoE's EQ money comes from the higher level players. The reason for this is that all those lower levels will, theoretically anyway, become higher, perhaps even uber levels. That being said, they do pay a surprising amount of attention to the lower levels from time to time, as DreadLord pointed out. TSS was a great addition. Of course, I imagine that SoE knew that they would eventually put out an anniversary edition that would attract many new and returning players, so an expansion that focused on the early levels would be a nice idea.
I often leave the game for months on end. I either get bored and do other things, or real life keeps me from playing, as it does many. I own only one account, so I don't multibox. I just cannot justify paying for subsequent accounts for a game, even though I do have three computers at home and could easily afford umpteen accounts. That is not trying to slap someone who does own multiple accounts, it is just my personal preference that I do not.
So, when I returned after my last EQ hiatus, I was happy to find TSS addressed my need for a way to level my new toons without rehashing Everfrost, Qeynos or any of the other newbie zones which I knew like the back of my hand. Sure, the game is still much the same in that you pull, whack, nuke, dot and loot, but at least there was a change in targets and quests for the lower levels.
Still, there comes a time in the life of every toon that we venture into more intense environs such as KC (either one), Burning Woods and beyond. In other words, even though my first return toon is only a few weeks old (real time), I don't really take him back to Crescent Reach or The Moors any longer. Those first few levels, since most players scream through them, really only addressed about, again as DreadLord pointed out, 5% of a toon's time. In a sense, we are ALL moving towards end game; some of us, albeit more slowly than others.
It is nice to know, if I ever stick with a toon long enough to get there (which is entirely doubtful, given my history), there will be something beyond just a banner which reads "THE END".