Once you become an adult, you're usually not exposed to straight-up bullying as much as you were as a child. Kids have so little control over where they spend their time. If their fellow students are harassing them, it's not like they can just leave that situation. Sure, some kids leave schools because they're being bullied, but that's awfully uncommon. Whereas if you're an adult getting bullied, you can simply leave: Follow the gospel of Tyler The Creator and log off!
Unfortunately, adults can still get bullied in the workplace, which can make for a hostile work environment. One woman recently went viral for telling the story of an older male coworker throwing her book into a bucket full of mop water. While the solution to this might sound obvious (tell HR immediately), she's getting a lot of resistance from her small team who doesn't want her to report the incident.