As for why I like Gentoo, unlike Arch/Artix it lets you configure compile flags while installing (just like FreeBSD when compiling from ports collection for the first time), which is tiresome, but gives you lots of extra control.
But compiling from soyce only makes sense in an era where developers could actually write code properly (it was the case when Gentoo started), nowadays though, good luck spending an entire week compiling Ungoolagged Chromium, just to be outdated by the time the compilation is done...