1. It’s presumptuous of me to assume that you own software that will be able to interpret the document’s format.
2. If I merely wanted you to read the contents a format such a .pdf is much more universally acceptable and there is free software you can use to open my document.
3. If I want to interact with you on the document, I have no way of knowing you are working on making changes.
4. If I suddenly realize I want to make a change, even while you have the baton (file), I want to be able to make changes to the document.
5. If it’s necessary to invite other people to give feedback, there’s no easy for us to all coordinate making the changes and ensuring we can all see the most current revision.
I will, however, gladly send you a link to something you can work on in your browser and we all have access to the latest revision in real-time. This is the future.