I suspect they would have some kind of backup. But, show me where they guarantee the user no loss of data. It could be there is such a guarantee. Also, there should be the ability to maintain backups from different points in time.
By the way, I like all of Apple's cloud services. They've made a lot of progress. I only jumped in because one point posguy99 made was being dismissed casually.
Backups are critically important to me. I rotate through 4 full clones, maintain 3 time machine destinations, and have offsite backup using Arq to two destinations. I do this from my main work Mac, which I consider the definitive source of all data that I care about. If I were to ever to start using my iPhone more seriously, creating documents stored in iCloud and never opened elsewhere, I believe there's a very real chance that none of my backups would catch all such files.