I was on a part of the web the other day that was discussing portable applications for Linux. In other words, there would be no need for the super user to install these types of applications. I can see where there already exist such things, as if someone were to create some interesting project in shell script or C/C++.

Why do most applications require superuser permissions for installation?

I figure it's a security issue.
But is it not still a security issue when a user has full access to compilers and the use of programming languages?