Put it this way.
5-20 years from now, who are you likely going to remember more and who will cause your eyes to light up and for you to smile the moment you pick up the phone and realize it's them (or if you bump into them on the street, at a wedding/funeral, in a restaurant, on vacation, etc.):
(a) The guy/gal you did mock interviews with in the "consulting club" or "private equity club" or even your fellow officer in that club, OR
(b) The guy who helped you learn how to skate in the Ice Hockey Club as you fell on your ass over and over, or the group of people you learned skydiving with in the Mile High Club, or the guy who you played drunk basketball with in intermurals
Join the "professional/industry" clubs merely to get on their email lists where you can get job postings that are emailed directly to the club.
But spend most of your time on the "fun clubs" because that's where you will develop the long-lasting relationships (or should I say friendships).
You are more likely to help a friend than a "business contact". That's what networking and relationship-building really is about.
Why do you think so much business no matter where you are in the world is conducted over a meal? Or on the golf course, or sailing, or doing some sort of leisurely activity? Because it's that medium that allows you to really connect with the other person on a human level. It's harder to do that in the sterile environment of a conference room or office building.
It's these very human and so-called "lesiurely" or "social" activities where you really forge trust. In the west, it's usually sports - golf, seeing a basketball/baseball game, etc. In Asia, it's the karaoke bars and other "extracurricular" activities.
Developing a level of informality with the other person even if you're both "working on behalf of your respective companies" matters. It matters in geopolitical diplomacy, it matters in the corporate boardroom, and it matters in school.
"Having fun" is NOT a waste of time at all. If you're focusing only on formalities and functional things, you are missing out on what business is *really* about - not just in school, but in your career.