Akira wanted to end it all with Cell. . .or even before. . .but NNNNOOO, editors and fans kept pushing and pushing and pushing for the series to continue.
It's always bugged me: Vegeta originally described the Super Saiyan as a legend which appeared once in
a millennium, & there was only 1 kind. Yet within a generation of that exposition -- every living Saiyan can easily become super, & they keep discovering new levels.