I think some people are operating under the impression that 4e skill challenges are always rigidly scripted. They aren't (or at least, the rules don't say they are; I certainly saw examples of scripted skill challenges back when I played, and see below). They do list the skills most "natural" for the challenge, but there is text right there in the rules telling the DM to be ready for players to figure out creative uses of skills, and to "try not to say no" to them. Unfortunately, there
is a bias toward those "natural" skills in that if players want to use other, "secondary", skills, the rules explicitly impose limitations on their use, and state that the DC for them should be hard, regardless of how well the creative use of a skill actually applies to the fiction.
Also, although not in the procedural rules, the very first example of a skill challenge describes how use of certain skills is needed to "unlock" use of other skills. That
is perilously close to rigid scripting, and I think it was a huge mistake to set that precedent as one of mechanics over fiction.
And so, I can easily see how the impression got out there that skill challenges are scripted with little room for player creativity, especially if people just say, "I roll Diplomacy" (because it's on the list of approved skills), without bothering to explain what their character says and does and how that
applies to the fiction in order to justify the mechanic of the die roll (
including the DM considering the player's specific narration to apply modifiers to the skill check, which I don't think the rules even mention).
If anything, 4e is guilty of assuming a DM needs to prep skill challenges in detail ahead of time in order to run them effciently at the table. It could have left a lot of that out, and saved a couple pages of text—and then used those pages to explain better how to improvise and dynamically fit fiction to mechanics. I think 4e made some key mistakes in their design of skill challenges, which fortunately are easily corrected (just chuck out any idea of natural skills or skills that unlock using other skills, and wing it!), but the text definitely put some emphasis on those mistakes.
By the way, compare 4e skill challenges to Torg Eternity's dynamic skill resolutions. You have 4 skill checks that must be performed in a specific order (ABCD) within 5 rounds, and you can only perform each when their respective letter comes up on an initiative card. The fiction involved is usually provided in published modules, detailing
exactly what the PCs must do at each step and what skill must be rolled (rarely with alternatives). The initiative & player cards allow for some unexpected stuff to happen, but really the challenge itself is very rigidly scripted (and in several instances in the campaign I'm playing in, literally on a train

).
Edit: Fixed a typo.