No good reason to not have an avalung is you can afford it. Just by wearing one doesn't mean you are going to take more risks. I certainly don't. As mentioned above, if you are not using one because you are going to avoid avalanches, then you don't need to carry a beacon, shovel, and probe either. So don't bother with those items either.
The thing is, even the best avalanche guru's in the business get caught with their pants down from time to time. Guys who are conservative. The problem is if "it's steep enough to ride, it's steep enough to slide". You can reduce chances that you'll get caught in an avalanche, but you just can't eliminate it. So if you can afford an avalung, why not have one? It's not a necessary item, but I and several of my partners rock one. Better to have a gun and not need it...