Office Online has all the same features and is far less likely to disappear one day. Personally, I don't use MS Office, but for business, or any other morphing collection of people, MS Office feels like the safe choice.
There are some advantages like version control or everyone working in the same document with the latest data.
I've seen it dozens of times. Someone shares the wrong excel file then others keep working with outdated data. Or maybe they all share a file in Dropbox but someone didn't sync for some reason and kept working and generating changes over an old file.
The majority of people using Excel in a business environment at least sometimes use those functions, even if most don't actually understand them.
There is just about always someone in the office/department who "knows excel" well enough to use the Macro Recorder and occasionally tweak something in the code, and that's enough. So they get the task of automating the thing in the spreadsheet and then everyone else uses it.
Yes they do. Maybe not the majority of users but enough to be important. There are a lot of very smart and math savvy people who don’t know how to program but do very complex stuff in excel.