Often personal projects are for learning new technologies and applying them in a meaningful way. E.g. many people want to run their personal projects on Kubernetes to play around with Kubernetes and understand how apps can be operated with it.
I'll admit that Kubernetes Is a Surprisingly Affordable Platform for Personal Projects when your personal project is to learn how to use Kubernetes.
Well yeah, I'm sure the time/money will pay for itself when he's looking for a job. I know I look favorably at homelabbers during technical interviews and DIY is often the only time you can get exposure to $new_hotness at some jobs.