You can crash your car even while sober. And you can arrive home safely even while drunk. You don't have "complete control" over whether you crash. But the responsible thing to do is exercise what control you do have. Yes you could catch and spread the virus even after vaccinated but it is still irresponsible to disregard this and risk the lives and livelihoods of others. It is a trivial request and the consequences of spreading the virus are non-trivial.
Drinking and driving is banned because it increases the probability of causing harm yourself and others.
Neglecting to get the vaccine is discouraged because it increases the probability of causing harm to yourself and others.
Exactly the connection I was helping OP to make. Indeed the parallels are obvious when phrased like this.