[Kelet]

Is it necessary? Of course not.

However -- to some, me included, maintaining an operating system environment is somewhat of a hobby. Operating systems like Gentoo provide standardized ways to configure how an application is built, and more importantly it provides ways to configure what compile-time features are (and are not) included in the binary. While most people wouldn't find the effort worth the yield, there are people who spend years of their life meticulously making a ship in a bottle. People enjoy it anyway.

Another draw to Gentoo for me is the way they handle package management. You can stick to stable, and packages will be relatively well-tested and mature, or you can choose unstable which will offer you bleeding edge packages. You can also have a stable system, and mark only a few packages unstable. Not many distributions offer a system like that. They are usually completely stable, or don't offer a way to keep most of your system stable while letting a few packages be unstable.

I've used Gentoo for a long time, and my maintenance is nearly nothing these days. Few problems arise (a new GCC version breaks a program or something), but I've actually gained enough practical knowledge to go about fixing these problems rather painlessly for the average case.