Perhaps that's because there is one narrow exception. So-called credit repair companies are notoriously scammy. But there are "credit re-scoring" firms, accessible only through lenders, that can help clear up legitimate mistakes on credit reports that are dragging people's scores down. You can correct legitimate errors yourself. Credit rescoring companies can just do it a little faster because they have formal relationships with the big credit bureaus to do this.
There's one last misconception that's not a back breaker, but does bug me. Twelve percent of quiz-takers thought obtaining your credit score was free. Not so. Several years ago Congress mandated that Americans should have free access to their credit REPORTS, and you can see yours here. Credit scores are derived from the information on credit reports, so it's important to get your free reports and make sure they're accurate, but credit scores themselves are not yet free. Most lenders use the original "FICO" Credit score developed by a company called Fair Isaac, so that is the one I always recommend checking. It costs $20 and you get it here.