Why are stratum and stratum-mining doin things in such a complicated way?

[Remember remember the 5th of November]

Twisted seems to provide you with a LineReceiver out of the box, however slush has not used that in his projects, he is also using some "Application Framework" and Services in twisted, I honestly have no idea what they are or what they do, but why not just start a simple TCP Server, but instead does things in such a complicated way?

I plan to write a pool software from scratch in Python using LineReceiver as stratum is a line based protocol and TCP4ServerEndpoint for the server itself. Anything I should know beforehand on why I should or should not use this?