I've always thought that the point of video games is to do things you can't do in real life
What.
Like, war games? We can do that in real life too. It's not about what is possible in real life. That's not what games are about at all.
I kinda get the core idea, but that applies to fiction, not games. Why make fiction about how your neighbors live their life, if you can have fiction about wizards and dragons.
So. What is a game? There are many answers to that question.
Doing things that are impossible in real life, makes the story of a game more interesting and exciting. But you do not need a story to have a game.
The root of games is playing. You play a game. And what is playing? From an evolutionary point of view, children and young animals "play" things that will benefit them in adult life. Better do pretend play with your parents and siblings, than get eaten by a real wolf.
So it is kinda funny to me, that you assume that one plays things that cannot be done in real life, as the actual roots of playing is exactly the opposite ;-)
To answer your question, Why play sports games when you can play sports?, because, well, you are a developer, are you not. You might be familiar with this image here https://en.wikipedia.org/wiki/The_Treachery_of_Images
But why an individual plays a specific (sports) game will always be answerd with: because it's fun. Also, that's not mutually exclusive. You could play a video game about the very sport you do in real life. And some people actually cannot do lots of sports physically. And most people could not compete in professional sports. Or the sport is too expensive. The list could go on for a very long time... ;-)