I haven’t read too much about this so apologies for any mistakes.
Basically it makes each user’s home directory portable, so you could load your home directory on a usb stick and use it on a different computer. Moreover, there’s the option to encrypt each user’s home directory. Currently, even if you enable full disk encryption, there’s not really a point if you share the pc with someone else (who you don’t fully trust). Once you unlock the disk, all data is out there for the taking (unless specifically protected). Or am I wrong about this?
Edit: So by default it seems that your home directory can be read by other users, but simply doing something like chmod 750 <homedir>
should fix that, but this also can be bypassed if the other user can get to know the root password. So encryption still is stronger, as even root won’t be able to do anything about it I think.