Gentoo Linux is a Source Based distribution that ask users to compile all software. While it gives a sensation of control, software compatibility is very restricted and their repositories have a lot of software that is out of date and incompatible to install on Gentoo, without facing more problems on compilation time. The Unique aspect of control that can give, it to those users who know the work of LFS aka Linux From Scratch, and want that process automated, while LFS don't face so much problems installing software.
After that, Gentoo offer the possibility to manage compatibility in Software, using the USE flags, that are "words" defined on the software, pointing into the compatibility. For example, Vim on Gentoo, can be installed without the Graphical interface, by adding something like this: app-editors/vim -X. With that value placed in the correct path /etc/portage/package.use/, as a content of the filename of the software(vim), Gentoo knows that Vim, will not have Graphical compatibility.
It simplifies the process of installing software without personalizing it with the core options that the authors give. In fact, all that painful process of extracting to / or other path each library and applications, ./configure --help Options, that can be More deeper than what Gentoo gives to users, and the make & make install to install software, can have extra options too. Since Gentoo wish to simplify that process, Gentoo serve that purpose only .
A interesting aspect between Gentoo and FreeBSD, is that Gentoo change the magic words of software compatibility when compiling, while FreeBSD don't care what "software compatibility" you want, when compiling software from ports. The "reconfig" option when compiling software using FreeBSD ports, is the best option to save you time. Else, you will need to Monitor compilation process, waiting for a new "popup" about software compatibility, of each extra software that some software ask as dependency.
In the other hand/side, Debian already compile everything and offer the same, almost all other Linux Distros offer: Binary Packages (already compiled software). What can take days (in case of using Linux From Scratch) or some hours (in case of using Gentoo) all other distros save that time for you, while software compatibility make use of all options available on each software.