While 90% of trauma claims in Australia are down to the 'Big 4' (Cancer, Heart Attack, Stroke and Bypass Surgery), these are not the only traumas that can affect you. The reason that these claims make up such a high percentage is due to younger people not tending to have trauma cover at all.
Workplace accidents and vehicle accidents do not discriminate on age! These can result in accident related traumas such as paralysis, major head trauma, severe burns, loss of limbs and coma. Also, the average age for diagnosis of Multiple Sclerosis is 31! This incurable, degenerative decease can take up to 40 years to kill you making it a very expensive medical condition.
So, if taking out trauma insurance is something you think you don't need because you are too young, it may be time to re-evaluate your requirements.