Teams from all the other countries including Pakistan's biggest enemy nation India are happily going to Pakistan to play cricket.
They trust the Pakistanis.

Then why only the Australians are not going to Pakistan?Is it just because Pakistan doesn't provide much earning opportunities to Australian cricketers as compared to India and England?

Security of the players is the biggest concern! Pakistan is going through a political crisis, and there are always some or the other things happening there....I think the Aussies don't wanna risk their life for a small sum of money! But personally, i think the show must go on...

Australian people generally do not know much about our south Asian countries.Pakistan they think is a country where a bomb can explode anywhere and anytime and that's reason why they are concerned about touring Pakistan.
India even though also suffers from these bomb blasts but we still have a better image in people's eyes as compared to Pakistan.It's all about image.
No country is safe from terrorism.If Americans couldn't safe the world trade center then what do you expect from developing country like Pakistan?Since America's image is good,even if 10 bomb blasts occur their people will still go to US because it's in their mind that US is a safer place.
Sadly many people do not consider Pakistan a safe place and Australian cricketers are among them.