I have an iPhone specifically because I want to use Google services (Calendar and Hangouts) without associating my entire phone with my Gmail account. A few Android releases ago, I was able to create a new Google account for my phone, with no contacts or anything, and still use Hangouts. It's recently gotten aggressive enough that I'm pretty sure that all my photos, location history, contacts, etc. are visible to my Gmail account and that my Gmail account has permissions to install apps on my phone, so I gave up and got an iPhone, where the only apps that care about my Google account are the Google apps I choose to install.