I'm vaccinating this year for the first time, due in large part to the programs that I'll be working on with my new flock(s).
I plan on starting a small business selling eggs, produce, crafts/goods mostly at farmer's markets around the Bay Area, I wouldn't want to take the risk of spending so much time and investing so much into an egg laying flock only for half of them to catch the disease and die off, essentially ruining the business model.
I'm also going to start specific breeding projects that deal with pure bred birds (that I have invested financially in) and I would not want to see those programs go to waste either.
I feel like it's something that should be done on an individual basis only, if you feel like it's necessary, then it probably is. If on the other hand you don't, then I wouldn't worry about it. The home I recently purchased has sat empty for almost 10 years, only having one previous owner before I bought it, (built in 1926) who knows what's in the ground? I'm going to do everything necessary to ensure that I've done what I can to protect my birds when moving to their new home. The earth hasn't been touched back there in a long time, however there is abundant wildlife that could potentially carry different diseases. So for me, I feel it's necessary.