Because in reality you probably won't get 70% more value out of the experienced candidate.
I was a fresh graduate once. I remember my productivity less as "60% of that of a twenty-year veteran" and more as "It is a miracle that they allowed me into the room for a purpose other than to empty wastebaskets, to say nothing of permitting my code in shipping products".
For that matter, I don't think I had 60% of my current productivity as recently as 2-3 years ago. I can still see my first commit at the day job in the repository. That code is an offense against God. It took me two months to get working the first time and then another two years of squashing periodic bug reports. (Unit tests? What is a unit test? Is that something you do with Subperversion?)
My product's code, particularly the parts of it which were laid down earliest, is so bad in some points that I wouldn't pollute a repository with it if I were rewriting today. Oh, God, the print logic. I can quote one line out of that file by memory:
I know a developer who was learning two new programming languages and started writing serious production code within three weeks of starting his first job post graduation. He took over maintenance of a complex application and rewrote it in a new language. He managed to double his salary 18 months into the job. There risk in hiring someone unproven, but you can buy that down quickly.
The point isn't that they produced something shiny, but the quality of the code that backs it up. The link you presented did not link to any source code, but to a marketing blog. The quality might be horrible, but they shipped it.
I was a fresh graduate once. I remember my productivity less as "60% of that of a twenty-year veteran" and more as "It is a miracle that they allowed me into the room for a purpose other than to empty wastebaskets, to say nothing of permitting my code in shipping products".