Because, if they announced it and it seemed plausible or even possible that they were correct, then every media outlet, regulatory body, intelligence agency, and Fortune 500 C-suite would blanket OpenAI in the thickest veil of scrutiny to have ever existed in the modern era. Progress would grind to a halt and eventually, through some combination of legal, corporate, and legislative maneuvers, all decision making around the future of AGI would be pried away from Ilya and OpenAI in general - for better or worse.
But if there's one thing that seems very easy to discern about Ilya, it's that he fully believes that when it comes to AI safety and alignment, the buck must stop with him. Giving that control over to government bureaucracy/gerontocracy would be unacceptable. And who knows, maybe he's right.
Our onboarding docs specifically tell employees to NOT use Google Authenticator precisely because of this issue. I have no idea how Google let this fester for so long, literally if even one (1) person over there was using it and got a new phone, they should have known about the issue.