If you're a business and you've spent 100 hours installing a piece of software across a network only to find updates and support drops a week later, that can work out to be very expensive.
You're also a very stupid business. It would be the exact same thing if you're a business and purchase proprietary software without a support contract in place. When that developer goes bust next week or decides to end of life that product, there isn't a single thing you can do about it.
Likewise if you're a student and a paper is due but you can't complete it due to a bug/error and the support section for the program you've used no longer exists, it's a big issue.
That is rather far-fetched. There are so many varieties of word processing and typesetting programs out there, many of them using open formats, that you will still have choices. What if Word starts crashing? You might find a workaround, you might be able to open the proprietary file in another word processor, but MS is under no obligation to provide you with support unless you pay for it.
Simply, F/OSS is not a business model, it is a development model. It is used to create a software product, a product which is provided as-is (source included), and is no different from proprietary software products provided as-is. Support is secondary in both cases, and paid for separately. Lack of support is not inherent or unique to OSS products.
All your files have been destroyed (sorry). Paul.