They're perfectly acceptable backup solutions for me; I've never in all the years that I've been using cloud storage across multiple platforms lost one file to corruption or to bad copies. Just because you have a problem with them doesn't invalidate them as solutions, and your position on the importance of backups doesn't mean that for someone else an iPad can't be their only computing device. Broaden your perspective beyond your own needs and desires.
That's a very common backup folly. "I've never lost an important file, so why do I need a good backup solution?" The answer is, when you need it, it will be too late. This is a timeless truth. It was true with Windows 95, it was true with OS X Tiger, and it remains true today. iOS is great, I love it, but it's not an excuse for having inadequate file backups.
I am confident that at some point soon iOS will have all the capabilities and features necessary for it to be a proper primary computer. Maybe it will be iOS 10 or iOS 11 (or iOS X as some like to suggest