Why did some Assyrian palaces use murals instead of carved stone reliefs?

In Assyrian palaces, mural paintings were substituted for carved stone reliefs primarily when a greater economy of labor and material was necessary.1

While stone was plentiful in northern Mesopotamia, the high costs associated with quarrying and transporting it led the Assyrians to treat it as a luxury material, typically reserving its use for specific architectural features and relief carvings. When these resources were constrained, or when a different decorative approach was desired, murals served as a practical alternative. For instance, while most chambers in the palace of Sargon II at Khorsabad featured stone reliefs, mural painting was preferred for the throne room. These paintings often adapted conventional motifs originally designed for relief carvings, though sometimes with less technical precision.213