No. Safety investigation agencies deliberately aren't regulators. The NTSB may decide that their recommendation is that every air passenger should be carrying a melon, and that results in a press release, a letter to the FAA saying that's what they recommend, that's all.

Deciding to change policies to effect the recommendation isn't their role. That's why you will so often see a safety investigatory body repeatedly recommend the same thing. The UK's RAIB (which is for Rail investigations) for example will often call out why a fatal accident they've investigated wouldn't have happened if the regulator had implemented some prior recommendation, either one they're slow walking or have rejected.

The investigators don't need to care about other factors. Are melons too expensive? Not their problem. Only unfriendly countries grow melons? Not their problem. They only need to care about recommending things that would prevent future harm which is their purpose.

> Deciding to change policies to effect the recommendation isn't their role.

And if it was the role of investigators to change policy, then there would be enormous pressure from industry to reach convenient conclusions, poisoning the investigation process.