If everyone was fully vaccinated then the diseases they are vaccinated against would soon die out*. This would mean there would be no more need for people to be vaccinated at all. Certainly, new diseases would be discovered and vaccines created but this would be a slow process.
If there was no more need for people to be vaccinated against current diseases then those companies who make money selling vaccines for these diseases would lose out. As a consequence, it is to their advantage for these diseases to continue to exist. Therefore, sellers of vaccines have a vested interest in a certain section of society not being inoculated and thereby harboring the fully-fledged disease. It may actually make sense for vaccine producers to encourage a certain fear in the community of vaccines to maintain a small proportion of dissenters. Without the continued existence of these diseases in unvaccinated individuals they would be out of business.
Alternatively, in cases of high vaccination rates, it is essential that vaccines are not too effective. If no vaccinated individual gets the full blown disease then the disease will soon die out making vaccines unnecessary.
This may help explain why vaccines are in some cases quite ineffective, for to be otherwise would destroy the very business of making and selling them! The same goes for all medicines, of course. To truly cure a disease in a simple manner would be bad for the business of treating the illness- which may explain why many chronic and deadly illnesses still have no cure.
*Assuming vaccines are highly effective at preventing the disease for which they are created.