1. Completely offline use, including local save, backups etc. Which goes completely against the cloud. But this is something that Microsoft got right with 365. I can install it and use it completely isolated from the internet and still collaborate online if needed.
2. Academic writing features, like citations, footnotes, and things like that. No alternative I have tried has ever been able to easily do these things, and MS Office has them all built in.
3. Suite interoperability. I need to be able to make a chart in Excel. Copy and Paste (Ctrl+C/V, not some export process) it over to Word in the document, then paste it into PowerPoint for the presentation. Or maybe save it out as a PNG for Latex or something.