I'm more bewildered to why no tablets seem to have multi-user functionality. In my experience, tablets get shared far more often than phones.
According to him, this is a feature that pops up once in awhile, but they have a long list of stuff to do and this is just one of those things that always gets bumped out.
From my perspective as a platform dev, I'd like to get into some of the technical problems with changing this, but I could end up breaking some NDAs or something. I'll just say, when you start mucking around with adding login code, file system changes, and the current dmcrypt encryption, you hit lots of fun design problems.
Single user login is a design problem! When I hand my tablet off to someone they have access to my gmail, gtalk, facebook, twitter, imap email, browser sessions and dropbox.
And that's just what I can recall on the fly.
That's the first thing I wondered about when Apple released the ipad: from the start, this looked like a family/eminently shareable device (and within a month you had reports of it being used as a shared family device, picked and left on the living room table for quick sessions of browsing or game), it felt weird that all the tablets were single-user, and the more time passes the weirder it is.
It only lists a subset of apps (automatically adding child-friendly ones it finds, but then editable) and prevents access to the phone functionality, redirects ad links etc.
It's not full user accounts, but a multi-user web browser. You can protect your bookmarks, logins & web history and it also has a guest mode.
Once you start adding stuff like login systems, seperate file permissions you start becoming a PC with a touchscreen.