With regard to this comment: there is nothing wrong with "spending time at a large company, benefitting from their experience in graduate intake, learning a lot of good, sensible practises, then applying them to a startup."
That is true. But there is also nothing wrong spending time at a small startup, learning good sensible practices, learning from smart people, learning from making mistakes, THEN applying these skills at large companies.
People often say "You'll learn a ton at amazon, then you can work anywhere." That is true, but you can also learn a lot if you work for a great startup.
The idea that you learn more at big companies is planted in students brains at these career fairs. And when GS and BofA come to campus to recruit. The idea spreads because startups don't come to campus and preach the reverse.