Spin back to ten years ago and Silicon Valley wasn't wholly reliant only on institutional knowledge and skillsets were earned through work experience. Hiring a stereotypical computer hacker that's also a social misfit rebel was because those were the ones possessing the skills that colleges didn't teach.
My boss while I was at the big fruit company told me stories about how back then, back when it was still a garage startup of the literal sense, if someone showed up, poking around, and asked for a job was given some job to do. If they lasted and are competent they were hired. Only the true nerds came around, because only true nerds cared about computers.
That's not true nowadays.
Now that the body of knowledge has been collected and distributed, now that the lead time has diminished and colleges are teaching skills in almost real time, a college degree has a benefit of sorting those capable of finishing a 4 year project and those that don't.
The lambda between two candidates, one that earned his stripes while on the job while the other having a degree, has diminished. In that case, why risk it? No one ever got fired for investing or hiring an Ivy League grad.