So to report a mental state, one must express one's thought that one is in that state. For many conscious states, there is something it is like to be in those states. And it might seem that perceiving our conscious states would help explain this, since it seems that there is typically something it is like to perceive things. But there is something it is like to perceive things only when the perceiving is itself conscious. Learning a new vocabulary for subtle sensory distinctions typically results in new sensory qualities' becoming conscious.
Conspicuous examples occur in wine tasting and musical experience.
The best explanation is that the new vocabulary enables us to have more fine-grained HOTs about our sensations, so that those sensations come to be conscious in respect of more finely differentiated qualitative properties. The same explanation extrapolates to less subtle differences among our conscious experiences, and even to the difference between an experience's being conscious or not. HOTs are responsible for there being something it is like to have our conscious experiences. There is another reason why a perceptual theory of consciousness has traditionally been favored. Our perceptions of things normally represent things as they are.