Google isn't doing this out of the goodness of their heart. They're expecting to make money off of every signup in some way. Directly or indirectly. If they want to continue their dominant status, then they should be responsive in some way to their users.
Sure, they have the right to cut off users any time they like. But it's ultimately self-destructive. Once trust is lost, it's difficult to regain it. I've moved away from my Google dependencies as much as I can, and have urged friends and family to do so as well. I'm only influential with around two dozen people, but once you start multiplying people like me by the millions, then Google has a problem.
And I'd argue it's at least a little immoral. Their services, especially Gmail, were set up in a way to make users highly dependent upon them. Google wanted that dependency for their path to near-monopoly status. To suddenly cut them off without the option of support or a clean exit creates real world chaos as the users try to pick up the pieces. Your email address might not be used much socially these days, but it's crucial for business contacts. For logins and customer interactions. The loss of it can cause serious damage. Google may not be legally responsible for the damage caused by a user's loss of their free services, but they're arguably morally responsible. Maybe they should pop up a warning to everyone using Gmail: "Don't rely on us. We're not going to do anything to help you if you can't use it one day."