Google has two reputations: The first is for its industry-leading, wildly useful Internet services and technology. The second is for collecting and compiling untold amounts of personal and private data to quantify and sell to advertisers.
You can't really have one without the other - many of Google's most useful services are effective precisely because they learn so much about you from your data. That's why you have to make a choice: you can accept the good with the bad, and trust Google (and its terms of service) not to do anything shady with that information. Or you can ditch Google services for the many alternatives.
Unfortunately, it's not always that easy. If you use Gmail, you know Google algorithms are scanning your personal information to tailor ads and automatically sort your emails into categories. If you've chosen to reject Gmail, Google is still "reading" many of your emails, you just don't realize it.