The question was asked, and has been thoroughly investigated at this point, but the administration did not like what they heard so they're pretending they never got the answer. It's childish and embarrassing for them to continue pretending that the question is still open.

Unfortunately we have many examples of debunked theories that maintain a public consciousness for a very long time. MSG, Flat Earth, Vaccine induced autism, Creationism, etc... All it takes is for motivated people to refuse to accept the evidence and continue repeating unfounded claims as if they were still valid. They can do this until they grow old and die, and there will always be at least a few people who follow.