Google and the company that made your phone are tasked with keeping your information secure, but so are you. Doing your part is easy enough; be diligent about the things you download and install, and make sure you have a secured lock screen with a strong backup password or PIN.
Google and the company that made your phone don't have it nearly as easy. They both need to make sure bugs and vulnerabilities are found and fixed, and the relevant software updates are filtered out so you can install them.
