High-level engineers can have more influence within the company and often earn more than directors and VPs, and most developers who want to move up the ladder don't aspire to become a director or VP -- they'd rather be a Distinguished Engineer, Fellow, etc.
Microsoft was generating cash by writing interpretors before they brought a VC on board. They only brought in a VC for advice and not money - so they still count. Although Gates' mother also had a lot of contacts in the Seattle upper crust. I doubt Gates needed Harvard outside of finding Ballmer.
Apple got VC funding though contacts made on the job not at school. Jobs went to a Liberal Arts college for less than a year. The Homebrew Club also had a big impact on early Apple. Several members of the Homebrew Club founded companies and they all kept track of each other.
Similarly with Oracle and Larry Ellison. Ellison spent some time at two Chicago universities but his contacts and training were largely on the job.
It used to be that having Harvard on your resume did not mean much in tech since it was not considered a tech school. The feel of the valley changed when John Sculley took over Apple since he was not at all a tech guy. This is just based on my gut, but I saw more Harvard alums after Sculley then before Sculley.
So I looked up the top schools for tech CEOs. This is the ranking of schools with the most CEOs with first round of funding. There were a few surprises for me. 1. Stanford 2. UC Berkeley 3. U of Pennsylvania 4. Harvard 5. MIT 6. Cornell 7. U of Michigan 8. U of Texas 9. Carnagie Mellon 10. IIT
Stanford and Berkeley were not a surprise since I have worked at a bunch of companies founded by Stanford and Berkeley alumni. IIT and MIT were also not surprises.
One thing that skews the results is that a bunch of schools provide masters programs to already successful professionals - so it is not clear that they actually contributed to the success of the alumni.
I know many folks who have went on to leadership roles in SV without degrees. It does matter who you know, but that matters even with a degree!