The Russian artillery units on Earth have never been motorized; they often use dozens of packhorses to haul four 76-mm anti-tank guns and their accompanying ammunition carts.
The Russian heavy artillery units have also never been fully equipped with trucks, maintaining a large number of mules and horses—just like the Sturmtigers' artillery.
Therefore, it's a bit unfair for military enthusiasts to mock the Sturmtigers as the "Sacred Mules and Horses Empire" all day long. In reality, only the U.S. Military was completely free from reliance on mules and horses during World War II; other countries depended on animals.
The Sturmtigers also have their say; at least their anti-tank artillery units have achieved motorization—to keep up with the Armored Divisions and Armored Grenadier Divisions.