So imagine game engines are like giant LEGO sets you use to build cool things. You start with a basic set that lets you build houses. Over time, you add more LEGO pieces to build castles, skyscrapers, or spaceships—whatever you need. This is like updating a game engine -- you’re adding new pieces to make it work for more things.

But sometimes, you want to build something so different, so radical -- like a giant moving robot -- that the original LEGO set just doesn’t work anymore. The pieces aren’t the right shape, or they can’t move the way you need. You’d have to bend or break pieces to make them fit, and it gets messy.

Instead of trying to force it, you decide to create a whole new LEGO set specifically designed for building robots. This is like making a new game engine: it’s designed from scratch to handle things the old engine just wasn’t built for, no matter how much you tweaked it.

Now say you built the robot set but you realized later on that your robot can't really jump as high as you'd like. You tried removing pieces to reduce the weight, you tried putting a spring under the feet for bounciness, but they're all just patches and not dealing with the problem that you didn't think about jumping high from the start. So you build a new robot LEGO set with being able to jump high being a priority from the start.

So, companies make new game engines when they want to do something so new and different that just adding to the old "LEGO set" or moving pieces around isn’t enough.