Here's why: http://www.nongnu.org/lzip/xz_inadequate.html http://www.nongnu.org/lzip/xz_inadequate.html tl;dr: Because apparently some people believe that not

Here's why: http://www.nongnu.org/lzip/xz_inadequate.html http://www.nongnu.org/lzip/xz_inadequate.html tl;dr: Because apparently some people believe that not only can they afford to exclude some users by avoiding zip's, but they must also bike-shed some more.