Except, CS graduates have no idea what it means to work in a corporate environment. I didn't - I learned about Big-O notation, binary sorts and searches, and lots of algorithms. I didn't learn how to navigate corporate politics, PCI or HIPPA regulations, the reasons security really matters, or how to write software which needs to survive for years past the deadline.
Perhaps even worse, recent college graduates going straight to startups are unlikely to find mentors to work alongside; they end up working without safety net, someone who can help soften the impact of their inexperience and facilitate catching bugs when the cost to fix them is 1x, instead of 100x. I didn't know how to take critiques of my code as critiques of my code, not my baby.
If they're successful, and their company hires people with experience at growing businesses, their world will be turned upside down as their projects are taken away from them and they are relegated to smaller and smaller roles (or worse, be promoted to management). They will go from being the star to a cog, and many will find it hard to accept; it will slow the company's growth and make the transition more painful than it needs to be.
I once had to walk a developer from a 4 year old startup through the hows and whys of separating variables from code. They knew and had experienced the pain points of having hard-coded values everywhere, but were unaware of the best practices and didn't know where to start.
I keep saying "cog" as if it's a bad thing. It's really not - the machine can't run without someone filling the role you fill. And yes, you are somewhat replaceable, but you knew this. That replacability is why we can job hop the way we do. And if you're willing to accept this, you can make the most out of it. Learn from your betters, hone your skills by mentoring others, replace yourself with code, and move on to something more challenging. Or, once you have the experience, create/join a startup, understanding what the future holds if you succeed.