Because it's not.
Spacing them out means they're getting some later, leaving them vulnerable longer. It also lends false credence to the idea that they're dangerous. In many cases, it may also mean kids miss out on the later doses, because repeated doctor visits to administer them may be unaffordable (copays) or difficult (scheduling, transportation, etc.). Multiple visits for shots also exposes them to germy pediatrician waiting rooms more frequently.
You state that such a discussion should not occur, and that those new parents should not have access to those (including our pediatrician, by the way) who state that the current schedule is much too aggressive and can safely be spaced out.
Denying new parents the opportunity for such a discussion is pure and simple arrogance and it does nobody any good except the egos of those who engage in that censorship.
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Whackadoodles. Nice. The arrogance is strong in this one.
Your own linked article (about not a study, but merely a survey whose demographics and actual questions are hidden from us) states that parents concerns should not be dismissed. This is a discussion about censorship, and you've shown yourself only too willing to engage in it.
The word I like to describe all of this stuff is scientism -- it looks like science, feels like knowledge, but it's just well-formed nonsense.
You don't agree that giving a vaccine later means you're not getting its benefits as quickly?
You don't agree that three pediatrician visits is 3x the exposure to the germs in a pediatrician's waiting room?
As for your pediatrician's particular practice, they may simply be avoiding conflict: http://time.com/3726887/doctors-space-out-vaccines/
> And while nearly 90% thought that such spacing out of the immunizations would put the children, and the community at risk of spreading infectious diseases like measles, 37% said they agreed to do so often or always.
(There are also a smattering of whackadoodles in any profession...)