PPPs are a new term for old concepts. Much infrastructure started under private auspices. Then many governments nationalized the ventures.
Governments often push infrastructure providers to keep prices low. In emerging markets, the price of water covers maybe 30 percent of costs on average, that of electricity some 80 percent of costs. This renders public infrastructure ventures dependent on subsidies. When governments run into fiscal troubles, they often look again for PPPs, and price increases. As a result, PPPs keep making a comeback in most countries, but are not always loved.