Keeping your chats secure is a good idea, but end-to-end encryption is just the beginning of the list of options to consider when picking a messaging app.
Govs have their own apps, email servers, various other web-based tools to exchange data, etc. Usually also gov hardware (ie can’t use/access such gov apps on non-gov phones).
It’s not “what’s better” it’s what is mandated/required/the law.
Much like when you get a regular average job you have to use whatever is permitted - company email is the usual, can’t just deal with company data over your private email account where the company has no oversight.
Anything that logs all the communication.
Govs have their own apps, email servers, various other web-based tools to exchange data, etc. Usually also gov hardware (ie can’t use/access such gov apps on non-gov phones).
It’s not “what’s better” it’s what is mandated/required/the law.
Much like when you get a regular average job you have to use whatever is permitted - company email is the usual, can’t just deal with company data over your private email account where the company has no oversight.