I think its because their international season overlaps. Would be nice to have Anderson, McCullum, Guptil and Munro. I don't like the idea of having a team from Asia in the Big Bash as some guy recently suggested, but it would be nice to either have Kiwi players in the current setup or maybe a team from there join the league. But the problem with latter is that it will probably end up being the Kiwi national side, which I don't like the idea of.