Why is awc still listed?

Read this at Intelligent Investor today

"Alumina is arguably the strangest large business on the ASX. Boasting a market capitalisation of $6.5bn, its sole asset is a 40% stake in another business, AWAC, which is the world’s largest producer of alumina and bauxite

That the business exists at all is an oddity. Spun out from Western Mining about two decades ago, it was made independent specifically to tempt larger miners to buy it."

I have held AWC on and off since it was split of from WMC, and I always expected it to be taken over at some point.

Does anybody know why this hasn't happened?