Kangaroos mainly die due to a lack of nutrition, getting killed by other animals such as dingoes, foxes, eagles, cats, human activity, and becoming victims of diseases. Mortality in kangaroos is furthermore affected by bushfires.
The good answer is yes, you can pat and feed kangaroos at Featherdale Wildlife Park Sydney. In fact, Featherdale is one of the best places where you can do something like that in Sydney and New South Wales.
Kangaroos use their strong tail and hind legs to stand up and fight. When they are in an upright position, kangaroos start the fight by grasping the neck of the other kangaroo with their forepaws. In this high-standing posture, kangaroos extend their claws and wrestle. They paw their opponent's chest, neck, shoulder and head. Some kangaroos then balance on their tail and kick the opponent’s abdomen with their hind legs.
It’s tough to see wild kangaroos in Sydney, you might see some wild kangaroos or wallabies in the outskirts of Sydney, for example at Western Sydney Parklands or Garigal National Park. The best way to see kangaroos in Sydney is to go to Taronga Zoo Sydney, Featherdale Wildlife Park or Wildlife Sydney Zoo.