Perhaps they thought it would cause too much of a rise against them? They don't want people fighting the government, but fighting each other. That's why masks are perfect, you can immediately form an opinion on someone based on their mask status and one group in particular thinks the other is trying to kill them.

Let's not pretend they needed the passports to track you, they can already do that. I was expecting them to morph into a China-like app system where they use the vaccine app to tell you if you're allowed to do anything or not. I'm more expecting vaccine-proof variant scare to hit instead. Extend the control a little longer.