As a writer, I appreciate the portability of bringing my work with me wherever I go. I can write an article on my Mac then transfer it to my iPhone to polish it up while I’m waiting to pick the kids up from school.
I also routinely transfer my photos and videos from my iPhone to my computer for storage.
Although you can now use Handoff to start work on an iDevice and finish on a computer, the feature requires a late model Mac running OS X Yosemite and an iOS device running iOS 8.1. However, it's also fairly simple to transfer files from a Mac to an iPhone or vice versa with iTunes and AirDrop.