Why don't we use Viruses to Fight Diseases for Us?

Antibiotic resistance is becoming a big problem, some strains of pathogens are now resistant to all antibiotics normally used in hospitals. But there is an alternative, using viruses that infect bacteria, bacteriophages, to fight the battle for us. This isn’t a new idea, in fact, Phage Therapy predates antibiotics; and for a time was greatly effective and uses in the Soviet Union. So why did Phage Therapy not find use in the west.