Well that would apply to a lot of thing governments spend money on. I think the idea is that governments are better at allocating capital in certain cases (obviously one might disagree with that) than the people/companies who generate the most tax revenue. I mean on an individual level even if solar batteries are profitable people who have sufficient disposable income might chose to invest it into the US stock market (if it still offers better returns) amongst other things than into something that benefits the Australian economy or society.