Why only 8 episodes?

[JHyde]

It's all sorts of things. Money being the main one, both for the cast and crew and also for the networks.

In Australia, it's a mix. Drama and comedy tend to be anywhere from 6 to 13 episodes as a rule (there are a few exceptions, including a long running medical drama Genevieve O'Reilly worked on for a few years) whereas other things can run once a week, 40 weeks a year.