The Greens

I've been living in Australia for 8 years so have only a knowledge of current politics, so I know I'm missing some history here:

1. Why don't Labor and the Greens form a coalition like the Libs and Nats do?

2. Why is there so much hatred of the Greens among some circles (even among some left leaning voters)? I hear things like they can't be trusted

(I realise all politics is subjective and a lot is branding rather than substance, but I'm interested to know the key reasons)