Not necessarily. Depending on what you're using it for you are able to detect any change in a player's gold/lumber, so in some cases it may be easier to do it this way. There is no real down-side to using a damage detection engine either, though, if it's going to be included in the map then it might as well be used for this so that there is record of exactly how much gold was obtained, and other data that you cannot reference from event responses.