I think the idea of proper maintenance of motors is a good thing. But, as with my Malibu Maxx car engine, there is simply not a lot of maintenance that you can do on a modern outboard. Oil changes, belts, if you have them, lower unit oil and impellers and that is about it. No real magic to it. After that, the engine works until you get bad gas, or you hit something, or you suckup a wad of garbage bag and so on. And of course, there is the issue of the engine just quitting because something lets go.
In the Malibu, I pull off the side of the road and call AAA. On the boat, I'm closer to being an airplane than a car when the engine gets poopy (tech term we learn in rocket science school) and I'm a victim of where a liquid medium wishes to take me and whatever the medium wishes to do to me.
Engine failure on a boat is a matter of when not if. That one "when," particularly on big inland waters and the ocean, can be a real bad experience.
I've read lots of books on water safety, boat handling and accident records. Coupled with my own experiences over the last 50 years, not having back-up propulsion on a recreational boat, small or large is gambling with safety.