You can intuit how much “active time” it will take you, personally, to do something. How can you intuit how long a task is going to spend in a queue waiting to be worked on because your team doesn’t have capacity, or another team “down the chain” doesn’t have capacity?

We have queuing theory because people are bad at intuiting the latter, and I don’t even think we're anywhere close to good, as an industry, at intuiting the former.