Deploying Piwik to your server can take a lot of time, and possibly be problematic. This is because it consists of thousands of files, which is a nightmare for poor old FTP.
So, since most servers run Unix, why not wrap the program up like so:
In this way, one would upload those two sub-files to the server, and then have nothing to worry about, because you could just execute Piwik.bash from your web-browser (provided you placed it in cgi-bin).
Not everyone has SSH access you know!