It's not that employers don't care about your hobbies (actually, for the most part, they really don't). The real reason to leave your hobbies off of your résumé is because the space on your résumé needs to be used in the best possible way to show off how you're a great candidate for the job. Your comic book collection is just not relevant when applying for a management job.
"But I want to show them that I'm a well-rounded person with varied interests and a stake in the community," you might argue. That's admirable. Save it for the interview -- and only if they ask.
There are exceptions to every rule, of course. Maybe it's a management job at a company that produces comic books. Maybe your hobby of researching and cataloguing historical documents is relevant when applying for a job as curator at a history museum. But 99 percent of the time, employers don't need or want to know about your hobbies.