There is also a theory that attention "disorders" are an adaptation or variation in novelty seeking. i.e. some people are just more wired for novelty seeking

Having a population with varied amount of attention seeking seems beneficial for finding the "optimum" for the local environment. Too much novelty seeking and the seekers will all get eaten by bears and starve because they fail to do what is known good. Too little novelty seeking and the known good will rot and be inflexible to changing conditions. (obviously contrived)