Honestly, 'earn it' sounds overly sanctimonious and is not nuanced enough to explain the sum total of everything it takes to succeed in this context.
While I applaud and admire those who've 'earned it' without - or despite - a non-prestigious school background, I agree with the premise that Silicon Valley organizations have a preference for hiring and promoting folks from prestigious (top 10) schools. Here's what a degree from the Top 10 will do for you:
Open doors because you'll have a network of people who are already in successful (and powerful) positions
Give you a halo effect. This reassures employers that they are hiring 'the best', in addition to boosting their brand value since the dubious 'talent quality' metric is for real.
Silicon Valley is an unprecedentedly attractive place to be today, and there's a huge influx of talent coming in. Top 10 graduates are turning away from Wall Street and the Big 5 consulting firms and coming here instead.
As for skills, a lot of those can be learned on the job. So instead of optimizing for 'who can do the best job', hiring is increasingly optimized for 'who will look the best doing it', especially for entry and mid-level roles. I regularly see folks from the Top 10 schools with degrees (and experience) that are somewhat unrelated to the expertise their job requires. In other words, a more experienced person with a non-stellar degree may be a better fit, but s/he is likely to be trumped by someone from the Top 10.
Finally, Top 10 graduates tend to be much more confident and self-assured (it's a virtuous cycle) and are generally good at personal branding and selling themselves. Obviously, that helps.
All of this is not to say that folks from non-brand-name schools are doomed to be unsuccessful. But they sure have to try a lot harder to prove themselves today in Silicon Valley. No wonder almost every prestigious school these days offers some sort of degree or certificate that (for a significant price tag) can 'enhance' your LinkedIn profile.