How many news stories are there every day about a politician or a celebrity tweeting about X? Just because it isn't monetisable doesn't mean it isn't valuable to the right (media, probably) organisation.
Perhaps the gossip magazines should pool their money and buy Twitter?
That power can be used to make massive amounts of money.
Right now you're suggesting that e.g. Disney is buying Twitter, for 17 billion dollars, to implement an untested business case. The cost of failure in that case is at least the purchase price of Twitter, that seems like a massive gamble.
I don't think Twitter is worth $17bn, but we live in an era of excessively hyped up and unrealistic valuations, so I have no idea what the correct price actually is. Yes, buying Twitter is a gamble, but many acquisitions are.