Between them, they have exact positions of a vast majority of individuals, at least in western societies. They could have done useful contact tracing at the press of a button, even historically, for every major event such as large concerts, churches, night clubs which we know were the most important situations to contact trace. They could have done this with the data they already have.
This would however set a bad precedent on how this data is shared. Law enforcement is one thing, medial tracing is another. So instead they set out to build this BLE tracing toolkit, which is something that at best is intended for future use, when everyone has the requisite hardware and software installed. It wouldn't reach more than a minority of users today which severely limits its usefulness, all for the possibility of reaching into situations such as bus rides, where nobody really knows how contagious these situations are because we simply do not have enough knowledge of the virus yet. Real world measurements are also likely to be noisy (where someone carries their phone in their hand and another in their backpack with a water bottle) even if we could set a hard limit on a safe distance, which we can't.
So maybe we will get something useful in the future, for the price of not exposing the data already available today.
It is amusing that the BLE tracing toolkits were sold as a way of not having to expose your location data to Google and Apple, the exact entities who already have fine grained location data on most people.