Above all else, it's because core functionality is frequently broken and issues like this[1] languish for months and years without updates. When things don't work, it's rarely transparent to users whether this is due to a bug on Element's end (or on the server side), user error or misconfiguration, or operator misconfiguration.

Further, there's virtually zero documentation for end users. There are no in-app explainers as to what E2EE is or why anyone should care, leaving the onus on operators to document and explain these things to non-technical users.

[1] https://github.com/vector-im/element-ios/issues/3762