A successful CEO once told me: "I like to nab brilliant engineers right out of college, and pay them well so they don't leave. In the end it is much cheaper." I both agree and disagree with this approach. On the one hand, he is showing concern over retaining the members of his engineering team. Frequent turnover is costly and painful – believe me, I've dealt with years of it. On the other hand, following that anecdote alone narrows the opportunities for the diversity on the team.
The best team I have ever worked with was diverse in many ways. There were young, enthusiastic, and energetic recent college grads as well as experienced veterans who could chip in with wisdom nuggets from timeless pitfalls they navigated on now-extinct technology stacks. As the wisdom trickled down, the energy and wonder of the younger members trickled up. There were engineers with backgrounds in Unix-land, Windows-land, and Mac-land and in web, mobile, and embedded systems. They were continually learning from one another. As a team, there seemed never to be a problem for which they couldn't generate a multitude of possible solutions.
While it is tempting for an organization to focus in on the fresh, bright minds, there will never be a replacement for the contributions from a team of many backgrounds. Diversity is just one of the many things engineering managers consider when building out a team, and I have enormous respect for those good managers whose magic I have had the privilege of witnessing.