Hobbies are great things. They help us figure out how to spend our free time. They help us unwind (hopefully).
They also allow us to find ourselves. When you find a hobby, it’s like finding part of yourself. It’s giving yourself the opportunity to do something you enjoy, and might not be able to do otherwise. It’s possibly finding a hidden talent or passion, and then working to grow it on your own terms. You can then decide whether to do it as a past time, or to incorporate it into your professional life by finding a way to weave it into your current job or change your job to make use of these newly uncovered skills and interests.
Hobbies are also great networking tools. These days, very few hobbies are completely self-contained, even if the activity itself is. Forums, message boards, and mailing lists have probably been set up for every single possible topic you can think of (and maybe some you wish no one had thought of), so it’s become easier to find others with similar hobbies and interests. These communities provide the members with several resources, plus the opportunity to be a local expert themselves. Meeting people with whom you have something in common leads to authentic conversations, a hallmark of good networking. (Naturally, there are people who still manage to come across as smarmy in these situations.)
While it’s still advisable not to put hobbies on your resume, you can incorporate them into your interview practice to help reflect who you are, to possibly build a bridge between yourself and the interviewer.
While hobbies are really for relaxation and self-expression, never forget they have other practical uses.