Because you seem to think shaming is about me feeling better at a huge cost: "you get an additional 15% uptake. Let's say you do shame, you only get 5%." I just don't think those numbers are at all accurate. I don't even think that the causation "shaming -> less vaccination" is true.
You don't understand human nature or yourself. Shame on you. Did that make you change your mind? Didn't think so.
I'm sure persuadable people exist, just what percent, I don't know. There are millions unvaccinated in the US and it will change over time. Many people are taking the "wait and see approach." If you don't understand why, see the Tuskegee Experiment. (https://en.wikipedia.org/wiki/Tuskegee_Syphilis_Study) All I know is shaming will have the opposite effect, assuming the intention is to get people to vaccinate. Shaming people is a very selfish and self centered action. The news does it all the time so you get that little hit of dopamine to watch more. Fat shaming is counter productive, lazy shaming counter productive, poor shaming counter productive, homeless shaming counter productive. Drug shaming is counter productive. Why on earth do you think it would it work now?
Bottom line, shitting on people is never effective.