You have asked a question that is likely to get a lot of different opinions. I called my county extension agent, in the phone book under county government, who put me in touch with a local expert on the subject. After discussions with that person, I elected to not vaccinate my chickens. That was for my specific location and the specific way I manage my chickens. Your conditions could be different so your answer may be different than mine. Part of that is what is prevalent in your area and part is how much you are going to expose your chickens to other chickens. I believe it is a personal decision with no one answer right for all of us.
If I see a specific reason, I will medicate my chickens. If I do not see a specific need, I will not. Do you take antibiotics regularly, whether you have a specific need or not? If you do that for your chicks, they will not develop some immunities they may need later in life. Do you occasionally treat yourself for the flu, even if you don't have any symptoms? I think a solid case can be made for regularly worming chickens, but I am not aware of anything else that I think warrants regular treatment without symptoms being present.
That is my opinion. I'm sure others will disagree.