The most obvious reason is that it guarantees the security and privacy of content being shared between users.
But this is not just limited to regular users: businesses can also largely benefit from E2EE, as it can protect sensitive data and information such as financial and legal documents.
News - https://www.thenationalnews.com/business/technology/2023/12/10/apple-study-shows-26bn-personal-records-compromised-by-data-breaches-in-past-two-years/