That's simply because Michael, owner of Phoronix, uses Ubuntu.
Well maybe because next to gaining more Linux adoption, it is simply the most widely know and widely used Linux distro for which the most proprietary apps are made?
If I didn't get such a newb-friendly, learning encouraging distro to hop onto something better I would have never used Linux as my primary OS in the first place.
If I have time to score a composite AV cable for the PSP and figure out what extrenal USB composite AV UVC capture card I can get and the nessecary drivers and a nice GUI app that I can fullscreen to play in realtime, it is bye bye for Windows. Not to mention Steam comming to Linux.
All thanks to Ubuntu.
Realy, I have tried and tried and tried to get onto the Gentoo bandwagopn because it was elite (always like to learn more) and because Gentoo was so tecnical I should be able to better learn Linux. In the end it was realy usefull for dual booting (wtf is hd0, etc...).
The preview iso images had a very bad installer. Once i used the manual mode to create a new partition (instead of using gparted) then i had a partition bigger than the disk. That of course lead to stupid errors like cfdisk no longer working. That's definitely not newbie friendly - hopefully thats fixed. The Kubuntu installer frontend is stupid too. I did not try dolphin, maybe somebody could test if it is now possible to mount partitions by clicking on em now like in gnome - using policykit (via hal usually for kde).
Ubuntu (or Mint) actually serves as a gateway to the Linux world, the way I see it. That's why its role is immensely important. Unless your nose is stuck up your arse you possibly cannot recommend Gentoo to someone coming from the Windows world, or just someone with no prior knowledge of computers. But if you tell them to install Ubuntu or Mint, and they're technologically curious, they might, with time, progress to more self exploration. But it's entirely up to them, unlike some brainfuck distros like Gentoo that (well, when I installed it it was like that...) force you to read their entire user manual before installation.
I've been through the Gentoo hell once, and the minute I had to wait, and wait, and wait for a frigging Mousepad or some other trivial software I needed at the moment to compile, I ditched it for something a bit more practical.