"Zero privacy" here means privacy from Google. Based on your reading of their ToS and your beliefs about their best interest, you may trust them to do no wrong and you may therefore be comfortable with Google knowing everything about your life, but not everyone feels the same.
Yes, sure, I know a lot of people who're not comfortable with sharing everything with Google, and I can understand that. Unfortunately, most of them are sharing their private data with some third party if not Google (that won't be any more careful about their privacy if they could mine the data as Google can, and probably technically less capable of preventing external breaches). In the end, it comes down to trust, one 3rd party or the other - as they're not managing everything themselves.
There's also a difference between having data here and there among many different third parties or sending everything to a single entity that can then collect in one place more data about you than what you yourself have access to.
