I think the description of 5e gameplay is incomplete to the point of being massively misleading. Granted, 5e does bad job of instructing the GM to how to do things, but still. The gameplay is about manipulating the fictional positioning of predetermined fictional elements in order to to put them in configuration that logically results success. Skill rolls are mainly used if the ability to manipulate a fictional element is uncertain. So it is not the GM arbitrarily deciding how many rolls are needed and when the situation is resolved; all this is informed by the fiction.
Skill challenges provide a fixed structure, which in certain sense is far more arbitrary. It just is certain complexity, and we need that certain number of successes. Whilst one of course should consider the fictional positioning under such structure as well, importance of it becomes weaker. The number of successes is fixed, and does not depend on how the situation evolves. You cannot solve the situation with one cleverly aimed roll or utterly botch it with a carelessly aimed one, regardless of whether that fictionally would make most sense. Or if you do, then you're abandoning the skill challenge structure, and are in the exact same situation than without it: the GM decides based on the fictional position that this was enough for total success/failure.