One of the most popular games on Steam right now is a game where all you do is click on a banana. The game is called Banana, and it is indeed as boring as it sounds. The game's popularity mainly stems from the fact that you can earn money relatively easily by playing it.
As mentioned, Banana simply involves clicking on a banana continuously. Over time, you get new bananas to collect, but occasionally a banana skin drops, which you can sell on the Steam Marketplace. Some skins are naturally rarer than others, resulting in different prices for each skin. The most expensive skin sold so far fetched over $1000, but the vast majority only earn a few cents.
Money is still money, and in this case, some even see it as "free money" because it's so simple. Currently, Banana is played by 700,000 players, though this figure should be taken with a grain of salt. According to the game's developer, who is himself suspected by some of launching the game as a scam to make a lot of money, the majority of these players are actually bots. This could lead Valve to take action soon to stop this "infinite free money game." Until then, however, Banana remains one of the most popular games on Steam, with more "players" than hits like Dota 2, PUBG, Apex Legends, and GTA 5.