Unfortunately there isn't a way to know ahead of time which complaints are frivolous and which aren't. They don't know whether the person who is calling in a complaint is a busybody worked up over nothing or if it's a jealous ex who wants a leg up in a custody hearing or if it's someone has misinterpreted what they've seen or if it's someone who has just witnessed the tip of an abusive iceberg. A quick visit by a trained professional is not particularly expensive and is much more effective means of data collection than a slow trickle of information from poorly informed and possibly malicious random people. Considering that this case worker is probably not getting pulled off a "real" abuse case to do this visit but is instead going when they have an opening in their schedule and would otherwise be idle, the claim it is drawing away much needed resources is questionable.