The strength to weight ratio of the best steel is better than the best titanium. Its just that most Ti frame builders compare Ti to bog standard Chromoly.
Steel is still used in the landing gear struts of military carrier based aircraft. Dispite the salty environment, only airmet 100 steel is tough enough for the task.
MTB ridgid forks are usually very stiff, and fat-tubed (like Pace Carbon). Steel is better suited to narrower tubed designs, ie a more forgiving, comfortable fork suitable for trail riding rather than aggressive sport riding. The downside of a very stiff, fat-tubes fork are most apparent in the repair dept. The fork is strong enough to resist frontal collision with logs, but the headtube is pushed inwards and the downtube buckles. Instead of a fairly cheap fork replacement, you need a new frame.