do they really want returns ?
Some portion of their investment is strategic, and may earn non-monetary returns that they would rather have than money.
But they do still need some of their investments to actually return money. Saudi Arabia's sovereign wealth fund might not be doing too hot right now, and has almost all of its cash tied up in illiquid investments (some of which appear to be at risk of going bad).
They've been quietly trying to unload some of their more liquid assets, and outsiders (and some reporters who claim insider access) say it's because they're running low on cash.
If that happens while oil prices remain low (or while they lose market share from artificially lowering their own production) they might not be able to afford to ride out these investments long enough to actually see a return. The whole thing looks financially fragile, and governments can only prop up bad businesses for so long.