Why isn't it sincere? Do you mean that if they were sincere, they'd stop the behavior?

Unfortunately, I think human behavior and relations are far more difficult than that. To a significant degree behavior isn't subject to will, though we like to assume it is. Everyone I know makes the same mistakes over and over (different mistakes for different people); they would sincerely like to stop. IME, to survive in relationships we have no choice but to accept those things in ourselves and in others.

Of course, that makes accountability very complicated, but I think it's a fact of life.