Maybe I'm wrong but you can't beat free...Besides, since FB is worth 112$ billion, it means it works. I don't think people care about privacy enough to pay a subscription. And don't think those websites are bulletproof.
Free definitely has its advantages. I guess it's more about awareness since many people don't really know the cost of free. But you could be right. People just don't care
What if I don't care about privacy?
Well then thats your choice. But the more incidents we have where people who don't know this end up being caught by surprise the more I think people will care and want another option.