Does anyone else do confidence votes?

Usually after sprint planning our scrum master will ask my teammates and I what our confidence number is. It’s 1-5 with 5 being most confident. If someone votes 1, the scrum master will give reasons why their vote shouldn’t be so low.

What’s the point of quantifying vague feelings like this? This seems pointless. What’s the point in talking people out of the way they voted? When our most senior dev doesn’t feel confident about the workload, I’d sure take his word.