For starters, they weren't happy with the server maintenance by WMF. They couldn't get essential components deployed for 2 years or so.
for every wikinews pageview there're 1600 english wikipedia pageviews. oh, and 60% of wikinews pageviews come from bots (wikipedias are at around 10% bot traffic methinks)
the only project less popular than wikinews is wikiversity and that says something.
it is much more rewarding to work on projects that impact lots of people ;-)
Domas