Why would you need someone with decades of experience to hire an intern or a new grad?

It's customary for a lot of companies to have an interviewer which is above or _at_ the level that you are recruiting. Therefore someone with a year or two of experience is perfectly able to hire an intern or someone that will be hired at the same level as them.

Looking at Amazon for example, "Hire and Develop the Best" is one of the leadership principles, and you CANNOT be promoted if you don't conduct interviews.