>Hum... Have you used them that way? And have you needed a project design to actually discover risks and estimate that you need to act on them?
Yes. These things are all over the place in defense.
One of the most important exercises in doing a Gantt chart is finding the "critical path" which is the set of tasks which can't slip without effecting the final timeline. If step two has two separate tasks that step 3 depends on, the longer task is on the critical path, the shorter is not because the shorter task can be delayed at least some without affecting when step 3 starts.
As the project continues you update the chart with what actually happened vs. your plans. The goal is to minimize changes, sometimes you can, sometimes you can't, but when there are changes you can see how the whole flow is affected and you can easily communicate the change in deadlines, changes in budgets, you can pull people off of one task and put them on another, etc.
In agile you do way less of this planning and the path is usually much more simple so you don't _need_ these tools to be successful.
