Invested / Endowed Value
Having already spent time and money to improve your status in the game, it's difficult to throw it away.
Game developers like to make you feel that the more you play, the more valuable your copy of the game becomes. If deleting the game and starting over from scratch sounds like a horrible idea and a waste of your investment, then the game has Endowed Value for you. The more time and money that you invest in the game, the more value it has over a fresh copy of the game.
Game developers usually accomplish this with a leveling system where you or your character get more powerful as you play. You may collect rare and valuable items or spend significant time collecting or building something that you don't want to throw away. You may have also earned or purchased cosmetic items that don't affect the gameplay, but make the game more personal to you. By customizing the game to be more personal, it feels more valuable.
Additionally, for games that require skill, the more time you play the more skilled you will become. This sense of acquired skill is important to people. It makes players feel good that they have increased their skill and it's difficult to stop an activity in which you are skilled.
The reason this works to the game developer's advantage is the "Sunk Cost Fallacy". This is often described as throwing good money after bad. The idea is that any time and money already spent on the game is attributed to the value of that game. If you spend $10 on a game, you may feel like the game is still worth $10 and it would be unwise to throw away something worth $10. And if you've already spent $10, what's another $2?
Likewise, if you invest 20 hours building a character inside a game, that 20 hours may have some value to you. You wouldn't spend 20 hours writing a book just to burn it, so why invest 20 hours into a game and then stop playing.
People have a strong aversion to loss. Most people would rather not lose $5 than to earn $5. When players feel like a game has some endowed value, it is difficult to stop playing and throw that away. It's this type of logic that keeps people playing the game even when it is no longer enjoyable.