Because EA does not port the full game to Switch due to hardware limitations. They reuse the previous year’s engine and only update visual assets.
Here are the details of the DLC Update 1 for FIFA 22 Legacy Edition on Switch: fifa 22 legacy edition switch nsp dlc update 1 free
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A Switch-exclusive mode that allows players to compete against those in their immediate proximity and track stats over a five-game season. Update History and DLC Because EA does not port the full game