Lack of need and practice, I suspect. And they may be prioritizing, but simply by different unstated (and perhaps subconcious) criteria than mere importance.

Lack of need and practice, I suspect. And they may be prioritizing, but simply by different unstated (and perhaps subconcious) criteria than mere importance. Someone struggling with an exam might first prioritize the questions they're confident in answering quickly to improve their grade. Someone who will ace the exam regardless of order can simply power through without needing to waste time "prioritizing" that could instead be spent on answering the questions. Someone who is smart/driven/competent enough to generally complete their projects in time and under budget has no need to prioritize features based on need - if they do prioritize, they may prioritize based on ease of overal implementation. That might mean prioritizing the "less important" / less defined items before the more important / more fleshed out aspects. Eliminating unknowns and variables up front in this way might lead to less time "wasted" on refactoring and redesigning.