Gentoo is a source-based distribution. The main benefit of using Gentoo is you pick features of a software you need to compile if its configurable. Here is an example I just saw:

% emerge -pvuDNt world

These are the packages that would be merged, in reverse order:

Calculating dependencies... done!
[ebuild   R   ] www-client/chromium-7.0.503.1  USE="sse2 -cups -gnome -gnome-keyring%" 0 kB

Total: 1 package (1 reinstall), Size of downloads: 0 kB

The developer just made GNOME Keyring dependency optional if you use gnome USE flag. That cups USE tag is an example, too. When Chromium just added printing support, they have made CUPS dependency necessary. It got fixed quite fast, in just a few days, Gentoo developer fixed it.

Note

I couldnt find an issue about it on Chromium issues, but it seems fixed in upstream because I dont see any patch in Portage tree.

Anyway, after CUPS, GNOME Keyring suddenly jumped out from nowhere. I already had GNOME Keyring on my system, but I didnt have CUPS. So, I let Chromium to compile with it, I didnt have a choice. Now, we have new USE flag.

If you are using any binary-based distribution, unless you try to build on your own or with some tools, your system is always with a bunch of stuff you dont need. And you never could have even a vague idea what have been made.

I still have some packages depends on GNOME Keyring, I should check them up again, some are optional, some might have no need to be on my system.

% equery d gnome-keyring
[ Searching for packages depending on gnome-keyring... ]
dev-vcs/subversion-1.6.12 (gnome-keyring? gnome-base/gnome-keyring)
gnome-base/gnome-mount-0.8-r1 (<gnome-base/gnome-keyring-2.29.4)
gnome-base/libgnome-keyring-2.30.1 (>=gnome-base/gnome-keyring-2.29)
net-libs/libsoup-gnome-2.28.2 (gnome-base/gnome-keyring)
sys-auth/pambase-20100310 (gnome-keyring? &gt;=gnome-base/gnome-keyring-2.20[pam])
www-client/chromium-7.0.503.1 (&gt;=gnome-base/gnome-keyring-2.28.2)
                              (gnome-keyring? &gt;=gnome-base/gnome-keyring-2.28.2)