That's fine for smaller chunks of work, and you're right that resolving uncertainty is not cheap. But if you're doing resource planning for a large organizatio

That's fine for smaller chunks of work, and you're right that resolving uncertainty is not cheap. But if you're doing resource planning for a large organization and you need to decide between high-value, long-timeline projects, that decision is irresponsible without some homework up front to validate the timelines. Large projects involve high- and low-uncertainty work and it's useful to do some of the former before spending resources on the latter. Your estimate still won't be right, probably, but the chance of uncovering an important problem is worth it.