It's not about the contract. AWS doesn't even have a deprecation policy in the contract - seriously, GCP provides more legally binding guarantees than AWS. It's about trust.
People look at AWS's track record, and trust that. People look at Google's track record, overlook what to an inside-the-company Googler perspective are dramatically significant organizational boundaries or product lifecycle definitions that are very poorly communicated outside the company, mentally apply reputational damage from one part of Google (or from a preview-stage GCP product) to a different part of the company (or to a generally available GCP product), and don't trust that.
Google has always been worse at externally facing PR than at the internal reality, even when I worked there (2011-2015). Major company weakness.
But the internal reality inside GCP, perceptions aside, is pretty good even now.
