Some states are more lax with anti-vaxxers, allowing for ambiguous exemptions. Other states, like NY, are more heavy handed - allowing only religious exemptions and barring unvaccinated children from schools if another child comes down with a vaccine preventable illness:
http://forums.anandtech.com/showthread.php?t=2388452
I don't know why people don't get why people don't vaccinate their children. If any medicine was as effective and safe as vaccines, we'd consider it, at minimum, highly unethical (probably child abuse) to deny it from someone that was sick.
http://imgur.com/a/ybBUJ
Short memories. As a species, that is.
That comic spells it out nicely.
Thanks in no small part to vaccination, the current generations don't have direct memory of what life was like before regular vaccination was around. We developed the technology to keep ourselves safe, but time caused us to forget the backstory.
I also get the idea that, when our species isn't facing enough immediate threats, we get paranoid.
Think of our evolutionary history: Tribal primates stuck in the wild, without the ability to store large amounts of information through the invention of symbolic written language. Your history lesson content was limited to the knowledge of the people living near you.
Living in the wild, there usually
was a threat out there. If there wasn't, that probably meant that the predator (or rival) stalking you was being unexpectedly stealthy. Or maybe a 20-year-long rainy spell was about to come to a natural end, and plunge the region into famine. Those who were paranoid about danger would have a better chance of surviving.
That paranoia persists, so we have things like witch hunts, or worry that antibiotics or vaccinations are the
real monster. Our short lifespans mean that our collective memory isn't so good, so we quickly forget how much things sucked in the past with regards to diseases.
(Side note: I still find it to be an impressive feat that we as a species have managed to largely eradicate some of these infectious agents. "We've decided that you are a serious threat to us, so we are going to remove your species from existence. Nothing personal though, so are we cool?" )