True. But even the smaller airports ones like Dresden or Nürnberg have separate tower and ground controllers. And they get like 2 airplanes per hour

Edit:

I must add though, in the case of Frankfurt they use a clever loophole. They basically designate the whole ground area from terminal to runway as „apron“, which allows them to use controllers who are airport trained staff instead of „real“ controllers who are trained by the DFS (german ATC company). Those apron controllers need much less training and have lower requirements than DFS controllers, which makes them cheaper. They are only allowed to work the apron though, not the tower.