Since we often work in a team on a presentation, it is crucial to be able to work on the same deck in two or more people at the same time (like in Google Slides).
This is a crucial feature making us to pay the next billing period.
There are plenty of software libraries out there that help sync data in real-time between users. But what happens when you want to give your users the ability to edit the same document simultaneously? They end up overwriting each other's data. So you end up either locking the document or abandoning the idea altogether.
Real-time collaboration is a term used for software or technologies that allow multiple users to work together on a project in real time, or simultaneously.