Companies are very, very risk-averse in hiring and they don't want to get stuck with one of those types. They overestimate the short-term risk of making a bad hire and underestimate the long-term risk of not moving fast enough or hiring enough.
Even from a purely cover-your-ass perspective, a manager who makes a bad hire will likely be blamed for not screening candidates well enough, but a manager who fails to hire enough can easily point to the "talent shortage". No one ever got fired for choosing AWS, and no one ever got fired for hiring an ex-Googler :)