Many novice writers try to avoid using 'said' by substituting synonyms: 'he uttered,' 'she murmured,' 'he questioned.' It's true that any word repeated too often becomes monotonous, but substitutions for 'said' can be worse than its repetition.
Words that add no new information or aren't repeated for emphasis are just padding. A sentence may carry three or five or eight of them, each one as unnoticeable as an extra two ounces on your hips but collectively adding up to a large burden of fat.