why people rare use xubuntu ??According Ubuntu, Kubuntu, or Edubuntu
Xubuntu is really good to use.

You forgot to mention Lubuntu, Mythbuntu and a myriad of others that don't get used as much a Ubuntu and Kubuntu.

Xubuntu is just a little ugly but show potential as it is the closest thing I have seen to replacing OSX's Agua. Also KDE and GNOME are the 'Pretty' ones, Kubuntu is the closest to Windows (LXDE is not enough for some) and the links to all of these other *buntus is deep in the Ubuntu website. Search Linux, Ubuntu, Ubuntu is the first link on ether the others not as close. Search Debian: Ubuntu is on the same page. And over the years Windows has drilled 'Piracy', 'Support', 'Cost', 'Compatibility', and much More into the users head. If they see that it's free then they freak out or (if they have used a program like VLC or GIMP) are fine. Ubuntu also 'fells' more linuxy (Windows: Bar On Bottom; OSX: Main Bar On Top; Ubuntu Unity: Bar On Left).

I think you need to check out Xubuntu 12.04 when it comes out.

I am running Xfce4.8 and it is quite a step up from 4.6 which is what Xubuntu is using currently.

Have Xubuntu 12.04-testing installed and running on here even, not bad for a testing release.

I am on Debian testing with Xfce4.8 and have been for some time. Has become quite a nice, if not flashy, mature DE.

The Debian usage I think is somewhat better, for me, Xubuntu uses a good many things borrowed from Gnome to "improve" it. This makes it heavier but many folks may prefer it to straight up Xfce.

I really like Lubuntu with the LXDE desktop. It is the lightest and fastest member of the Ubuntu family that still provides a relatively full featured desktop environment.
Although my hardware has enough muscle to run a full on Ubuntu with that smart phone wannabe interface known as Unity, I prefer a light and fast and simple system. So Lubuntu with a well chosen collection of lightweight apps suits my needs just fine.

There are many reasons why people might choose different versions of Ubuntu, or Mint instead of Ubuntu, or the ever growing number of Ubuntu-based distros that show up on distrowatch. The reasons I have provided here are why I choose Lubuntu.

Various reasons, a lot of them historical.

Xubuntu used to be very, very VERY heavy compared to other Xfce distros. In some ways it was heavier in RAM use than normal ubuntu for a while! So some people who would have used xubuntu used lubuntu instead (as lubuntu wasnt anywhere near as heavy in RAM use as xubuntu). The only people who ued xubuntu was the people who didnt like the 'standard' gnome desktop ubuntu, didnt like lubuntu, and didnt know about or didnt have the skills required to install xfce (without all the xubuntu-desktop dependancies)

Even though xubuntu has improved over the last few releases, its still got a reputation for being heavier than it should be, or needs to be.