12 months of notice is laughable for enterprise customers. From planning to getting something rolled out at scale, an enterprise will have eaten 2 quarters of time.
More than full deprecation, we often have API deprecation from google services, increasing our maintenance burden.
Say what you will about AWS or Microsoft products, if you build something on those platforms you know it'll be supported for a long time.
Google fundamentally values their own code above the code of people using their platform. But good platforms do the opposite - they keep the technical debt on their side of the fence to make sure you don't have to think about anything if your code runs on their stack.