I agree that parents should immunize their children against childhood diseases for several reasons.
The first one to be mentioned is that a child is a social creature living among people, being part and parcel of social life, i.e. children go to kindergartens, also along with their parents they go to movies, puppet-shows, circus, cafés, shops and many other places. Thus without being immunized a child is under great threat to fall ill of any of those serious diseases recommended to be immunized against, such as tuberculosis, chickenpox, smallpox, measles, mumps etc. Since children take active part in social life going to kindergartens, their parents are responsible not only for the health of their own kid but for all the other kids that can be infected by a non-immunized child.
The second thing I want to draw your attention to is that even if a child is not taken ill in the childhood, he/she can fall sick in elder age and this is more dangerous because the illness might take a wrong course with complications.
Child receiving polio vaccine.
A child receives oral polio vaccine during a 2002 ...
This Bangladeshi infant was being immunized, but ...In this connection doctors strongly recommend to immunize kids in childhood so they could get the immunity against the diseases mentioned.
Now there is a bad tendency of women to get taken ill with roseola while pregnancy period and since the disease can have really unpredictable effect on the foetus the women are strongly advised to have an abortion. Only the presence of immunity may help in this case. To my mind this is a good example why it is reasonable to immunize kids to facilitate their life in future.
We are living in a society and we are to protect ourselves and each other from bad effects that are likely to happen, so immunization is just one the ways out.