Also, we have a bias against overturning beliefs.

I think the folk epistemology implied in the distinction between words like "suspect," "think," "feel," "believe," and "know" is, on the whole, fairly useful. You can flatten them all into the word "believe" but you lose something. The dogma here is also to assign probabilities to your beliefs - the zoo of belief-verbs is just a cognitively cheap way of doing so.