I can't be precisely sure who these "some here" you reference might be, but if you're referencing the usual cast of characters in these discussions, such as
@pemerton,
@hawkeyefan,
@AbdulAlhazred, and
@Manbearcat, et al, I can provide a current example that demonstrates how patently false is your sense of how these games operate in practice.
In the second "encounter" of my ongoing 4E D&D PbP with the latter (a campaign that we, as players, set to focus around political intrigue, class strife, and dueling mercantile factions as the initial focus of play), it was suggested by a newly-encountered NPC (who has since become an integral part of the story and a Companion Character (think: Henchman)) that the Empress, who has initiated a fresh Inquisition that curtails some of the freedoms of my PC (and his mercantile family's goals) may be (1) possessed or otherwise bereft of her wits (possibly through nefarious advisors), or (2) a fool who needs to be set back on the "correct" path of rulership.
The game is now at L7, and much of it has revolved around dealing with the fallout of our group's early challenges to this situation (outsmarting one of the Empress's Dragonborn Inquisitors, deposing corrupt and duplicitous family members, investigating a revolutionary group and its aims, facing and making enemies with the Empress's Secretary of Security). There have been other goals in play too, of course: my wife's PC led us on a mountainous Quest to commune with a spirit of her ancestors when the political situation in the capital became particularly hot and we needed to "get out of Dodge." And there's an increasingly-compelling parallel development where agents of the Far Realm entity Caiphon lurk in the background (this too was signalled as a point of fictional interest by us as players, as the steward of my PC's traitorous uncle was a Warlock, and I introduced into the fiction that his patron was Caiphon, at which point
@Manbearcat and I discussed our mutual love for that particular trope and how we wanted to explore it more in play).
And yet, we still haven't even met the Empress, let alone faced her as a direct challenge.
We have felt compelled by other, more immediate (though certainly related) practical and fictional concerns that nevertheless have as an end-goal setting right what befouls the Empire (from my PC's concerns, the Empress's new edicts that curtail his family's enterprise and power). We've also discussed as a group how dealing with whatever besets the Empress seems perfect for a kind of capstone challenge to the Heroic tier (ie, 9th/10th level), taking the cues from 4E's guidelines regarding a tier progression of the focus of play to be local > regional > planar > cosmic. None of this has felt contrived or predestined. Rather, in the fashion of good film or writing, we see the PCs form goals, some of which change over time (as we "play to find out"), and work to meet those goals. If you're interested in seeing how this actually plays out, there is a meticulous record in our
play-by-post.