From Deep Look:
Cats' tongues are covered in little spines called "papillae" that look like tiny hooks. Cats use their tongues to groom and the spines do a great job of detangling knots….
Cats spend much of their day cleaning themselves- up to half of their waking hours! Cats are ambush predators and they need to stay clean in order to remain hidden from their prey. Prey species tend to be on the lookout for danger, and one whiff of the wrong odor can give the cat away.