There are very mundane reasons that you may want to own the software stack your data depends on that aren't 'I don't trust Google/Facebook/Microsoft/The Reptilians.'

The most prominent of which is "What happens when they drop support for my use case/lock me out of my account?"

Unfortunately, the cost of running your own one-off solution is rather high. And doubly unfortunately, while I would pay money for a box that I could plug into my computer that provided all of these services, I wouldn't pay enough money to justify someone building it, and selling it to me.