Well, you don't own any of the software you buy. You just purchase a license to use it and that's it really. I guess the lesson is that you have to consider the possibility that one day the software you use will cease to function. Nothing's guaranteed forever.
I use a web based scheduling/employee management/billing app for my business, and while it's been an absolute boon for me and made my life 1000% easier, it's always at the back of my mind that one day this company might go out of business and shut their servers down. Horrible if it happens, but unless you have the will and the $$$'s to commission your own software, it's something you should always consider. In fact even if you order bespoke software, you're still relying on someone else to maintain and/or update it, and what if
they go bust. Just a fact of life really. Everyone wants some kind of catchall legal protection to guarantee that nothing bad will ever happen to them but it's just not viable.