ZA, like the majority of countries before them (not just in Africa) consider having 'their own' carrier as a mark of prestige and a 'place marker' in the world. It is not just the snouts in the trough - they think that having 'their' airline branding makes them bigger on the world stage. As Europe, the Antipodes and the USA have discovered, this is no longer the case.
Once upon a time you had to have your shipping line, then you had to have your airline. Now? In due course, ZA will follow the rest of Africa in realising that they cannot fund an airline of the 1970s and 80s any longer. However, if they want to prolong SAA for a bit longer, they can ask Alitalia how they have pulled it off ....