Why are Kirkpatrick, Degrasse Tyson and others so vocal in their denial of NHIs, UFOs, etc?

Legit question. Are they simply hired and paid to keep keep that stance publicly? Are they just convinced that extraterrestrials can’t exist? I mean, there’s at least a 50-50 chance they exist and while they claim there’s no proof that they exist, well they neither have proof that they don’t exist. So there’s a 50-50 chance they’ll look like the biggest asses ever, I can’t understand why they’d risk entering history as the ones that didn’t see it coming