The concept of what I phone is says that is a bad idea. They removed that feature because of the need for security. It is primarily a phone and that aspect has to be front and center. There are Apps for that like files or dropbox. But the point is that users shouldn't have to search around to figure out what apps are compatible with what. For instance Android out of the box never supported PDF, Doc, or even vCard files even though these have been supported in since the second version of iOS or sooner. The next Android version is adding support but how many years have these simple expectations been unavailable with out downloading a special application. But customization is hailed as more important than having something so simple.
So I have to use dropbox if I want to access files and waste my data plan doing so as well? I could be wrong but I don't think dropbox is free either and limited on how many gigs I can have at X monthly cost. Nothing is quicker then accessing my storage on my device. I don't know maybe I'm old school but I like the option of having stuff on my actual device especially when I don't have a data connection or don't want to waste my small data plan. Until I can have unlimited data at a reasonable price I can't justify living in an entirely cloud type world.