Parts of speech

Why is the word "computerized" in the sentence "We offer computerized information services." a passive verb and not an adjective? Is it supposed to be assumed that the information "was computerized"? Can't the past participle (V3 form of a verb) simply function as an adjective? Isn't it similar to the use of the word "written" in the sentence "The written word propelled human knowledge.", which functions as an adjective?