A while back (before iOS 9) somebody argued to me that iOS does not need multitasking since humans can’t actually multitask, and can really only focus on one thing at a time.
What that person missed is that you can use multiple apps at the same time for one task. I could be writing a report while referencing a book. I could be drawing while referencing an image from your gallery.
iOS works great — until it doesn’t. I think everyone who uses iOS for more than the usual content consumption has at least one story where they failed to do something completely. For me it was transferring a photo. I had no internet access, and wanted to get a file from my iPad to my Android phone. Can’t do it! Of course, apparently it was my fault for not buying an iPhone, or for going on vacation somewhere without stable internet access.