They are useful for one job: comparing candidates quickly within a single tool's index. They are misleading for almost everything else, because they are logarithmic, they compress differences at the top, they ignore topical relevance entirely, and each vendor's number is incomparable with the others.
The damage they do is in link buying, where a high score becomes the only criterion and sites engineer the metric deliberately. A relevant link from a site scoring 25 in your industry is worth more than a generic link from a 70, and no score will tell you that — reading the site will.