I use it for the security as it is easily the most secure OS on the most secure phone. It also gets very timely updates.
And me (or thousands of people) not buying a Pixel won't exactly cripple the behemoth, or even make a dent in the bottom line. From what I remember, their hardware department is not where they make a lot of money.
Paradoxically, Google is the one Android manufacturer dedicated to device experimentation and security (and I stress security, not privacy) in a way that allows for a secure mobile os stack that's resilient to spyware or tampering. Graphene build on the security and privacy that few other OEMs match on Pixel.