### Brute force matcher vs knn+RANSAC, which is better?

Why are most articles that deal with comparing feature descriptors use the k-nearest neighbor matcher + RANSAC instead of a brute force matcher, especially that the brute force matcher performs all the possible comparisons, so he gives the best possible result. It's true that by doing so, the brute force matcher takes much more time the k-nearest neighbor matcher + RANSAC, but are there advantages to using the knn+RANSAC ?