Here's why:

* Detection Bias: Our current methods of detecting exoplanets are biased towards finding large planets that orbit close to their stars. This is because these planets have a stronger gravitational pull on their stars, causing a more noticeable wobble or dimming effect.

* Gas Giants are Common: Gas giants are generally larger and more massive than rocky planets, making them easier to detect with current technology.

* Rocky Planets are Smaller: Rocky planets like Earth are much harder to find because they have a smaller gravitational influence on their host star.

However, recent advances in technology, such as the James Webb Space Telescope, are starting to uncover more diverse exoplanets, including those that are smaller and potentially habitable.