Because People Holding Hands Across the Globe Was Too 90's
The logo for the Olympics is one of the first symbols we become familiar with as kids. Sure, we might recognize the McDonald's Golden Arches as symbolizing "ball pit," or recognize Chester Cheeto as "terrifying nightmare cheetah"… but as children we're taught that the Olympic Rings = Big Time Symbol.
So you can ask just about any first grader, and they'll tell you that the five rings that take up a large corner of our TV screen represent the five continents.
Wait. What happened to the other two continents?
Well, when Baron de Coubertin—the French aristocrat responsible for starting the modern Olympic Games in 1894—designed the image, he was using a loose interpretation of the "five inhabited continents" that included Africa, the Americas, Asia, Europe, and Oceania. (Source)
Ah. That explains it. It's an old, outdated symbol.
You might also notice that there are always five colors: blue, yellow, black, green, and red. According to Coubertin, the five interlaced rings of color included all the colors that appeared on national flags of the world.
But ultimately, the symbol of the Olympic Rings is supposed to represent the fact that athletes from all over the world have gathered at the Games to compete under a truce of peace and friendship…and no one can knock that.