But have you considered that’s what the “power-players” want you to think? Then, you won’t know to build rockets for yourselves and steal the resources!
Imagine being one of the people to make that measurement though... You're in the observatory with some notes and a spreadsheet to calculate the keyhole orbit parameters. You have a big stack of business cards from journalists wanting to publish the result as soon as you calculate it.
If you made the measurement and it... wasn't good - imagine the result of telling the world that life would end in 2029 - would you maybe be tempted to call the other scientists around the world and discuss whether or not to reveal the actual result?
We do have the technology to redirect a potentially extinction-level asteroid, so I don't think it would be all doom and gloom. More like a scramble to launch a redirect mission. (And besides Apophis isn't large enough to cause an extinction event, just destroy a country or two).