A mask is
1. A constant reminder of the presence of the pandemic.
2. Fallible in ways that humans can easily visualise.
Vaccines on the other hand are indistinguishable from magic.
For COVID-19, there is a known set of strains that hopefully won't change. So a vaccine targeted towards that set should work, at least temporarily.
The following is just me speculating: from what I have heard, coronaviruses are called such because of distinctive proteins on the outside of the cell that are hard for the virus to change. If a vaccine elicited an immune response to target such a protein, then it should be effective for all the strains.
And I think people will see a covid vaccine as more like a flu vaccine than an MMR vaccine.
This was so much part of the narrative that there were later pieces about how bad this narrative ended up being, e.g. in the NYTimes.
So for sure, it was a real thing.