Some people have to use these tools for work and need a version of Office that actually works. Good luck with say your accounts department trying to make to with "Sheets" lol.
Sheets is Google, Calc is LibreOffice. You've... never actually used LibreOffice, have you?
The big advantage of LibreOffice Calc is that it will open spreadsheets from SharePoint, which Excel frequently refuses to do because the total path length is greater than 218 characters. This, incidentally, has been a problem with Excel since 2010 and Microsoft keep ignoring it.
This is why I swear at Excel and by Calc, even for work.