People don't do things that are purely detrimental? How about...

Suicide, drunk driving, yelling at your boss, antagonizing people who might be armed, commiting crimes in places where you should know there are cameras, intentionally posting racist shit on social media where potential employers will see it, eating unidentified mushrooms, smoking crack, smoking meth, snorting cocaine, shooting heroin, speedballing, k-holing in a public place, shacking up in a public restroom, defecating in a public pool, fake attempting suicide just to get attention, autoerotic asfixiation, watching a Fast & Furious movie, having unprotected sex with strangers, getting a tattoo of your current boyfriend or girlfriend"s name, signing up for a variable-rate loan, mixing Viagra and MDMA, paying for extra lives in mobile games, eating fast food, putting things inside your butthole that you'll need a doctor to pull out later, trying to pet a dog that's growling at you, trying to wax your own ass, having "just one more drink" on a Sunday night, impulse shopping, and trying to get some of that earwax out with a Q-tip even though you know that's just going to push it further in and cause it to block your hearing on that side completely until you can get someone to squirt water into your earhole and flush out the earwax stopper you just made?