Yes, in this case you explicitly introduce the reader with context, which is important when you have specific information that may be considered sensitive, or history that is not relevant.

Anyone reading the "to" line can see where the reader was introduced.

I find workplaces that default to closed conversations, and require explicit reading in of new participants, to be poor places to work. It feels like people use connections, being involved in key discussions, and their ability to connect people, as social currency. This is good for them, bad for the rest of the organisation.

I find it great, it saves me from information overload. For 'project' things, these often start on a mailing list and I can go back/search a mailing list if its that important.

I'll be honest to say, most things that is said in any communication medium is a complete waste of time. Having i searchable rather than forcing it on people globally is the only scalable option.