For roughly the same reasons that I'm not using perl 5.8.x or 5.6.x. Also, while we're at it, the same reason that I'm still using Apache 1.x and mod_perl 1.x. It's because I've got about a million lines (give or take) of code running on 5.005_03 (and apache 1.x/mod_perl 1.x).
Not that we don't upgrade... we do. Admittedly, we're kind of behind with perl. We'd begun a project to upgrade to 5.8 late last year, but it unfortunately fell apart due to personel issues. It's coming back, but not the single highest priority at the momebt. But I digress.
The point is, I think that a lot of folks are not yet using perl 6 because they have jobs, and those jobs are using lower versions of perl. (Espescially considerring that there are most likely about zero jobs available using perl 6.)
Not an editor command: Wq