But how do I, the bouncer at the door of my local bar, know that you, some schmuck that walked up and wants to come in, have had the vaccine? What proof can you show me, that will make me comfortable you aren't going to come into my place of business and turn it into a superspreader event? The government can say anything it wants... enforcement requires transparency and data, and I don't see how that part is going to work.
It's a numbers game. There won't be any super spreader events if sufficient numbers of people are vaccinated. We just have to trust that the vast majority of people are going to act in their own best interest, which in this case is also in society's interest. Of course, convincing people what their best interest is is often challenging, no doubt.