Honestly, because I haven't yet taken the time to figure out how. Mostly that is because I have the feeling pip is more intended towards libraries and things used while programming python. Pagekite is not really a library (yet), it is more of a system utility, so integrating with the OS (rpm/deb and such things) seemed far more important.
Pip is by no means exclusive to libraries. See https://github.com/jkbr/httpie for an example of a CLI app that's distributed through both pip and easy_install.