Self-defense is an essential skill that every human should have. Even if it's minimal, the ability to intelligently navigate physical combat can provide one with a massive psychological boon. Instead of walking around with a heightened sense of insecurity, a self-defense practitioner feels infinitely more secure in dangerous situations. Plus, any student of a martial discipline learns an unspoken truth about reality: understanding how to inflict physical harm typically makes you less combative. Having a background in any marital discipline forces you to assess every person with a sense of humility. You discover that virtually anyone could have pugilistic skills and immediately gauge the physical costs of a potential skirmish. Someone that looks like a "pencil neck geek" might be a secret MMA master.
In the video linked above, Conor McGregor's official YouTube channel, TheMacLife, shows Mark Zuckerberg putting in some solid work in an MMA gym. I wanted to make fun of him, but, to be honest, his technique is actually pretty impressive for a civilian.