The problem was, undergrads in top 50 CS programs were not using IBM mainframes during the 80's. They were using UNIX. Same thing today (and a few PC here and

The problem was, undergrads in top 50 CS programs were not using IBM mainframes during the 80's. They were using UNIX. Same thing today (and a few PC here and there). Getting access to a mainframe was and still is very expensive. That's why Google, Facebook, everyone post 2000 basically got started on commodity hardware. Because it's cheap, it's what the founders knew and it works. It's also what the top 50 alumni know, and there's no vendor lock-in.