Defeating the Elite Four and the regional champion in battle is a rite of passage in most Pokémon games, and that includes Scarlet and Violet. These are supposed the most-powerful Pokémon trainers in the Paldea region, and overcoming them and their teams is the only way to become the regional champion yourself.
Source: Kotaku – So, You Wanna Take Down Pokémon Scarlet And Violet’s Elite Four