I recently tried the new Ubuntu release and when I wanted to change the cache setting of Ubuntu update, I noticed that the Synaptic Package Manager was no longer available.
Why? It was one of most useful applications in Ubuntu in my opinion.
You can read a short description about the reasons in the Ubuntu Wiki: https://wiki.ubuntu.com/SoftwareCenter#Rationale
Early versions of Ubuntu shipped many graphical utilities for installing and removing software: Add/Remove Applications, Synaptic Package Manager, Update Manager, Software Sources, apturl, GDebi, and Computer Janitor. This redundancy increased the amount of interface people had to learn, wasted space on the Ubuntu CD, fragmented development effort, and made people more likely to think that unsanctioned software installation methods were safe. Ubuntu Software Center replaces Add/Remove Applications, Synaptic, apturl, and GDebi, and acts as the main entry point to Software Sources.
Beyond providing a central point for installing and removing software, USC plays a small but important part in encouraging application development on Ubuntu, by providing application developers with a prominent way to offer their software for installation.
Synaptic was removed from the base install because it was made redundant by Ubuntu Software Center. If Ubuntu Software Center doesn't fit your needs, it's very simple to restore Synaptic by using a single command:
apt-get install synaptic.
For 2 main reasons:
Software Center was going to replace it. That is why you see Software Center with a huge change and look.
Synaptic and its dependencies use several megabytes of space that could be used for something else. The idea was to keep it tight in the CD format space.
This is not problem since you can always install it. In my case I also use
aptitude so doing something like this will give you
sudo apt-get install synaptic aptitude
Of course I udnerstand why you would want Synaptic. Personally I like the idea that if I type "nvidia" for example it shows me ALL packages related to it. Or if I want to install something from an not authenticated place it lets me. Software Center is safer in this matter since it does 2 things, removes from the search the packages that a user normally would not be searching for and does not let you install packages from a not authenticated place (It even tells you of it). Same goes for Update Manager.
But hey if you are 100% confident of the PPA then use Synaptic for it or if you want to find something specific that only 1 out of 2 million would search in the packages, then synaptic/aptitude/apt-get is for you.