Parents take the advice of people that know people that have a relative that read a story about some tenuous connection between vaccinations and a host of illnesses attributed to them. While I to agree that multiple vaccines given simultaneously may not be a great idea, I cannot subscribe to the notion that vaccinations are merely a means of “Big Pharma” to make boatloads of cash. Making vaccines is not a lucrative business. It is fraught with risk and liabilities. It's one reason why vaccines are no longer made in the US – the fear of lawsuits that would wipe out the company making the vaccines. The drug companies make far more money and take on far less risk making other drugs than they'll ever make manufacturing vaccines. But that makes no difference to those blaming Big Pharma for all the world's ills.
One of the biggest reasons given by parents for their decision not to vaccinate was the aforementioned belief that they can lead to autism. The argument goes that the rate of autism has gone up and that most changes seen in children took place right around the time they received some of their vaccinations. But autism tends to show up right around the same time in unvaccinated children. But that doesn't convince many parents and they choose not to vaccinate or delay vaccinating their children.
One of the effects of this has been the reappearance of diseases the vaccination were used to prevent, such as measles, mumps, rubella, chicken pox, and whooping cough. Some of these diseases can kill. It's only a matter of time before polio makes a reappearance.
The debate about the issue ran on in the comments to the article linked above, with some responses purely emotional, others purely scientific, and others with a pragmatic view about whether to vaccinate or not.
One of the best comebacks I ever heard by a doctor responding to a young mother's spiel about why she was not vaccinating her young child came from the TV show House (from memory):
Young Mother: “Oh no, I'm not going to vaccinate him. All it does is make huge profits for the drug companies!”
House: “Well I'll tell you another business that will make a fortune if people like you decide to 'stick it to the man' – the companies that make tiny little coffins for infants like yours.