VBA scripts. I have a friend who works in the radio/telcom industry...but ends up doing a bunch of other stuff. This friend makes extensive use of VBA scripts to get the job done. You can't do that on the web version, and you can't do it in Calc.
Word is just for document interchange. Other businesses and clients use Word documents, and they don't display reliably correctly in any other program but Word.
I don't use Microsoft Office, but I use Adobe. If the people I collaborate with or I work for use Adobe and need to edit my files, I'm not going to give them something done in Scribus instead of inDesign. That would be doing a bad job and also limiting their choices significantly with who they can go with in the future to edit their files. Same principle applies to Microsoft Office.