Sure, call me selfish, but it's just not worth it for me.
Now, if I have to go get it, or pay a $200 fine or something - yeah, I'll suck it up and go do it.
In an ideal world, all those who opt out should have to pay the medical expenses of those who get sick. Not vaccinating is the same sort of negative externality as environmental pollution.
Rather than making it a fine, a high opt-out fee could cover it without the stigma of "breaking the law".
Under your logic all those who eat fast food for lunch everyday and don't exercise should have to pay extra for medical insurance for not taking care of themselves.
Err, that's exactly what happens. Your premiums would definitely be higher if you live a riskier and less healthy lifestyle because you would require more costly health care at a younger age.
And as another poster pointed out, we're now also coming around to the idea of disincentivizing poor food choices for the same reasons, like taxes on sugary drinks.
So this is not "my logic", but in fact the prevailing logic of most people.