I feel this argument is like saying there's no point in developing free and open software because there are already other pieces of software that were adopted, and are de facto standard.
In my opinion, this actually promotes the development of technology to be shared for the benefit of everyone, not just to help with vendor lock-in.
If you are talking of MS Office... I am afraid that yes, the various free/open alternatives (especially to Word) were a wasted effort (of course, it could be that MS made their products more affordable in part because they were worried by the possibility that Open Office etc. could become "good enough" to make people switch, but honestly, this March I got a perfectly legal copy of Office for Mac for less than 75 USD... and I bought it because I was asked to prepare some slide for a professional group and I preferred to buy the whole packet out of my pocket than risking issues with "export to Powerpoint" from Keynote).
LibreOffice and other free and open source alternatives to Microsoft Office are definitely not a "wasted effort". LibreOffice is able to handle just about all of the home and small business use cases of Microsoft Office, and many people are able to skip buying Microsoft Office licenses because this free alternative is available to them. Also, Microsoft Office still does not support Linux outside its feature-limited web app edition, while LibreOffice does.
In my experience, the moment you bring a non-MS Office document to a meeting with people who pay you for the content of your document you are always risking to have problems/complains about one or more images going missing, the fonts acting strange, the print (either on paper or as a PDF) coming out wrong.
Granted, the latest episode was more than 5 years ago, but at 75USD for a local (i.e. non-cloud) licence I prefer not to take any chances.
Maybe "wasted" is too harsh a word, but I cannot say that in more than 30 years of work I ever found any real use case for non-MS documents.
If I am writing personal letters or putting together a few slides for, I dunno, my TTRPG campaign, everything goes, even Google or Apple stuff (both are free, the latter is free because it comes with the HW itself, if you use a Mac).
But when I know that there is a chance to get money for my document, the expectation on the customer's side is to get something that works with their Microsoft stuff, and I will comply.
YMMV of course, and I have surely missed any advance in Libre/Free Office for years. But as I said, I prefer to play it safe, and the cost of a licence is not really low.
An office suite is an essential tool that people expect to have in a computer. Being able to use this tool without needing to pay a license fee makes computing more accessible to everyone. While $75 (USD) might be affordable to someone in the U.S., the price for a Microsoft Office license is considerably higher in developing countries relative to average incomes. (Also, the U.S. retail price for a Microsoft Office Home & Student 2021 license is $149.99.)
Sure, if your employer or client expects you to use a particular piece of software, you're more than likely going to use that software to meet their expectations whether it's Microsoft Office or LibreOffice. However, many people use office suites outside of these specific business arrangements and LibreOffice is there for them if they don't want to pay that $75 to $150.
Tying this back to the original discussion about device connectors, if Microsoft ever neglects Microsoft Office like it once did with Internet Explorer, I can see alternatives eventually overtaking Microsoft Office in the office suite market just as Chrome overtook Internet Explorer in the web browser market. In the USB-C vs. Lightning situation, Lightning is the Internet Explorer of connectors, the proprietary connector that has a much lower maximum data transfer speed and much more limited device compatibility than USB-C. Although USB-C is now the de facto standard for device connectors, just as Microsoft Office is for certain business use cases, neither is guaranteed to stay that way forever. If the design of the USB-C connector is unable to incorporate some important technological advancement, it will certainly be replaced by an alternative just like Internet Explorer was replaced by Chrome and just like Lightning is being replaced by USB-C now.
Too late for edit: "cost of a licence is not really low" should have been "of a licence is NOW really low".
I do not really disagree with the points that were posted in response, anyway.
I just stated that "working in a country where MS Office is the de facto standard", all the other free alternatives (including Apple products - so it's not a dig against non-commercial products) are "not viable alternatives FOR ME" (special emphasis on the last two words).
In my opinion, this actually promotes the development of technology to be shared for the benefit of everyone, not just to help with vendor lock-in.