They seem to have run out of tanks about a year ago. They of course have thousands left, but they now have to consider the risk that a tank might be destroyed today and thus not usable tomorrow. They still use tanks, and lose a few, but they no longer take risks with tanks without considering the costs and so they don't use nearly as many as they used to because they want to preserve those they have left.
We generally expect the same is happened to artillery about now, though we don't know exactly when. They get to choose how many they will risk.