If you are reading the text of a person who presumably care about that person state of mind and what this person believes. If you don't why do you read the text in the first place?

I do think there a difference between someone thinking an event is unlikely with p=0.2, p=0.01 or p=0.0001. It worthwhile to put a number on the belief to communicate the likelihood.

If people frequently provide likelihoods you can also aggregate the data.