The arrival of Raditz brought the concept of aliens to the world of Dragon Ball. It expanded the scope of the series, allowing for more sci-fi-styled concepts over the more mystical flavor previous Dragon Ball arcs had. The world of Dragon Ball had changed irrevocably, and the more the story leaned into space and further beyond, the more appealing the concept of alien races seemed. With more new Dragon Ball stories coming out every day, it's no surprise that more and more alien races are being added to the mix.