having been raised by a pediatrician (and spending plenty of time in the office & hospital behind the scenes, and knowing other pediatricians and their families personally) I think have a bit of insight.
I know I was vaxed to the absolute HILT. my mom often tells the story of how incredibly relieved she was when the Hib vax came out because she saw so many children die of it during her residency. (as if she'd looked up all the bloodwork on all the meningitis victims and known it was HiB for each one of them!) my mother vaccinates herself, her kids, her family, her husband- a couple years back, he cut his hand on something and she gave him a TD- when I brought up that it took about 13 days for that vaccine to even work, she basically shrugged her shoulders and said "he's due for one anyways". siigggghhh.
it's not just vaccines. it's MEDICINE in general. they don't look at vaccines as some separate, controversial issue- it's part of the job, like anything else. an important part, at that. every day, they or their nurses administer hundreds of shots. sometimes, they get paged because a baby has been screaming uncontrollably or has a seizure. I'd wager it rarely to never even crosses their minds that it could have anything remotely to do with the vaccine. My mother has said to me "I have never seen a vaccine reaction in 25 years." When you don't know what reactions are possible, because you've never bothered so much as reading the package insert, and you were brainwashed from the day you entered med school that vaxes are safe, how could you see a vax reaction? You refuse to. To them, it's hysterical, ignorant, or religious nutcases who make a big deal about autism or brain damage and vaccines. They rarely to never come across well spoken, educated, and confident non-vaxing parents. And if they do, they'd just think "that parent might mean well, but they're wrong- I'm a DOCTOR and I know how important vaccinations are." They don't bother to remember that they don't actually know anything at all about most of the diseases prevented by vaccines, or anything about the vaccines themselves. They simply take comfort and pride in knowing they are part of the elite group of medical professionals and completely rely on major medical organizations and pharmaceutical companies to decide what is safe and effective. It's not a concern, it's not even worth thinking about- the vaccination schedule exists, therefore it is correct, and what must be done.
ignorance. groupthink. brainwashing. pride. denial. fear.
(disclaimer, yes of course there are exceptions, I'm only speaking of the average mainstream ped. Our ped is basically pro-vax but at least says it's the parent's choice, and doesn't give us a hard time.)