The car industry wasn't an essential strategic asset, vital to the national well being. Cars can easily be imported from multiple sources at a lower price, and dare I say it, better quality than they could be produced in Australia. Whilst it did provide jobs directly and also throughout the supply chain, the cost of maintaining those jobs was prohibitive. Given the limited local market and high cost of production the industry would always require support, and whilst everyone wanted Holden to be saved, few people actually went out and bought their cars. Ford Australia and Holden weren't going to become major exporters similar to Toyota and Hyundai so their prospects were very limited.
Qantas on the other hand is a strategic asset, particularly on the domestic side and can compete well with foreign airlines on the international side. It was previously profitable and will likely generate future profits once we are over the current situation. It may not even require a bail out if relative normality returns soon. Government resources will be stretched extremely thin in the coming months, if any aid is given to Virgin at all it will be very limited and conditional on the airline showing it can turn around in a fairly short time, which will require major restructuring and downsizing. Anyone who thinks Canberra will simply write a cheque which enables Virgin to continue in its present form is dreaming.