It doesn't need to be. Alhamdulillah I've been blessed with facilitating dozens of shahada and I always make sure it's done in the language the person understands best.
But most feel saying it in Arabic gives it a bit more "ceremonial gravitas" so I've never once had anyone opt to NOT do it in Arabic as well.
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u/Ok-Duck-5127 1d ago
Why is the Shahada always said in Arabic?