They still had to debase to pay their armies and magnates when they were fighting wars on two or three fronts (Bulgars, Pechenegs, Normans in the West; Arabs and later Turks in the East) and constant civil wars in the 11th century. Michael IV was literally a money changer before he became emperor by marriage. In about 80 years the gold content in coinage dropped by about 70% and eventually they had to introduce coins struck in silver and copper