Let's talk about compression rates

[S Mathias]

http://pastebin.com/raw.php?i=MwDnhknf

$ ls -Sl
total 461252
-rw-rw-r--. 1 g g 111709730 Jan 22 11:06 linux-2.6.37.zip
-rw-rw-r--. 1 g g  93174605 Jan 22 11:03 linux-2.6.37.tar.gz
-rw-rw-r--. 1 g g  73552510 Jan 22 11:10 linux-2.6.37.tar.bz2
-rw-rw-r--. 1 g g  66333786 Jan 22 11:16 linux-2.6.37.7z
-rw-rw-r--. 1 g g  64035788 Jan 22 11:16 linux-2.6.37.tar.7z
-rw-rw-r--. 1 g g  63480808 Jan 22 11:20 linux-2.6.37.tar.xz
$ 

I presume kernel.org knows this. Why doesn't people use e.g.: XZ?

This is the same as in PDF's. DJVU files could be amazing too. They could compress [convert] a 400 MByte PDF to a 20 MByte DJVU. Amazing.

Why don't these technologies spread??

Any opinions regarding it?

Thanks.