The current systems are full of limitations: http://0install.net/comparison.html
Thus why many projects have tried to improve the situation, but is now that a big distro is adopting such features, in order to better compete and take marketshare away from the main OSs.
Ubuntu in particular needs to separate core from apps:
Of course we need to help keep users within a centralized apps market in order for them to stay as secure as possible, but people keep going out to get 3rd party PPAs, etc. which can be a security risk too, so there's no secure situation right now either, just lots of fragmentation and user frustration with not being able to update apps without a command line that can usually break other software and replace libraries/dependencies. So this is to help with that.
Lots of trolls may say that ubuntu doesnt need or worse like its going to kill linux or something and that's BS.