Linux

They are extremely integrated into the rest of the ecosystem and are insanely pervasive among 9-5 desk jockies. They aren't gonna relearn a spreadsheet software especially when it doesn't have all the same features as the thing they have been using for 20 years. Not to mention they dont actually give a shit about how much their company is paying for it. The majority of these people dont know what FOSS is and are just using computers because that's what pays their rent.

Libre office is very far from being a drop in replacement for 365 and will most definitely never replace it. At the end of the day its all about userbase. Why do people still use twitter and Instagram even though there are FOSS alternatives that may be even better? Because that's what everyone else uses and most people just dont care.

It just does more and more easily. It styles things better, makes them more professional looking with a click. It can do certain things like nested tables in Word that Writer cannot do. Excel is much more powerful than calc, it has more functions, more refined functions, it's easier to work with, has more and prettier chart options. And oh you can create tables in Excel that are sortable. There are many other cases.

Now for the last two the die-hards will whine and whinge about how you should just use a software for creating charts and a database but sometimes you just want to make something quick, sometimes that's overkill for what you need. Grandpa doesn't need to learn how to deal with databases just to make a sortable list of books he's read, he can just use excel and the Libreoffice people telling him to pound sand because they won't add that feature to calc because it doesn't belong there means he and many other people don't use calc, they use MS office. Likewise the Libreoffice defense force saying of making graphs and charts to just use dedicated software, well many corporate types, business people, white collar workers don't understand those things and may not be able to get them installed, what they understand, what they already have is MS office and it works and has lots of pretty, professional, very slick options which don't make them look poorly in office meeting presentations.

Just on the sortable tables front, I can't tell you how many times I've run into hobby stuff that's based on an excel file with tables that rely on being sortable. From stat sheet creators to mini-databases (<2000 rows) on some game created by fans.

It's useful for those who need the very bare basics of being able to open and read basic MS word documents, csv files, excel files, and to write an occasional letter. But the moment you need to start doing beyond basic formatting or dealing with files that have that, you run into issues.

You have this gulf of usability, it's useful for people at the very bottom of the basic needs pole, barely computer literate types who think facebook is the internet and it's useful for highly technically competent people who can and do use other dedicated software, often without GUIs to solve problems, it's a frustration for the middle 60% of the population who are more than basically computer literate but not scientifically trained, not CS or IT.

Good question. I wish I had a better answer than what I'm about to say.

It just is.

I'm a diehard anti-Windows, Linux-lovin', FOSS crusader myself, but if Microsoft released a copy of MS Office for Linux (as a one-time-purchase), I would buy it today.

For most tasks, you're right, there's not much you can't do in LibreOffice. But the interface is clunkier. Excel makes it easier to make good-looking spreadsheets. And as much as it hurts me to say, looks matter when dealing with nontechnical folks.

Plus there are some things that are just more intuitive in Excel, like certain kinds of charts and graphs. There are some advanced features of Excel that don't even exist in LibreOffice. Like chart styles and certain team collaboration features.

Compatibility is... okay... For the most part, but having it all guaranteed by a bunch of paid devs would be really nice.

There is a more detailed list here

I'd be so bold as to say about 90% of windows business users are only using it for office/excel/outlook

Yeah have a great time supporting libreoffice across an org of 200/2000/20000 end users. Not happening. Not without a dedicated helpdesk team that ONLY supports users office troubles. The cost of that would be way more than their monthly 365 subscription.

Also theres the infinite number of comparability issues youlll run into if you need to do business with another company that only uses Microsoft.

Also nextcloud is great but it absolutely is not competition to one drive or SharePoint in the enterprise.