From a scientific perspective, it does matter. You may have heard the term "herd immunity;" a lot of people laugh at this concept but it is a real thing.
Imagine a group of one thousand people. Keep in mind that there are individuals who, for medical reasons, cannot receive vaccinations of for whom vaccinations are not effective - say for this purpose there are ten of these people in the group. Now consider if EVERYONE ELSE in this group has received the measles vaccinations. If the medically necessary unvaccinated only come into contact with other people in the group, what is the chance that they will get sick with measles? The answer is 0%, because there will be no one around to spread it.
Now imagine that there are also 100 other unvaccinated individuals in the group. They could received the vaccinations, but just don't. They, too, are mostly only in contact with people in the group. However, once in a while, they have contact with the "outside world." During once such contact, one of them is exposed to the measles virus. Then they go back to their group.
At this point, what is the chance that the people who cannot receive vaccinations may become ill? Remember that 1/10 of the population is susceptible to measles simply because they chose not to be vaccinated. If one of these people is exposed to the sick person, and becomes sick, and then passes it to the next one, the disease can spread around the community. The more sick people there are, the higher chance that another unvaccinated person will be around a sick person and thereby contract the illness.
If even 1/3 of those who chose not to get the vaccine got the disease, that would be 33/1000 or 3%. That is high enough that it could be very easy for any or even all of the medically unvaccinated to accidentally cross paths with an ill individual. Then a person who had no choice in the matter could become very sick, because someone else chose not to get the vaccine.
On the other hand, if the ONLY ones who were unvaccinated were those who could not be for medical reasons (10/1000), then even if ONE of those people became ill, the chance that they would come into contact with another such person would be very low and the risk that it would spread to ONE other individual, never mind ALL 10, would be very low. That is the concept of "herd immunity" and why it matters that everyone be vaccinated.