used to increase or decrease the alternating voltages in electric power applications. Electrical energy can be transferred between the two coils without the need for a metallic connection between the two circuits, as described by Faraday's law of induction.
Enables system diversity and galvanic isolation of circuits
Transformers are highly complex and add cost and weight to projects and equipment assemblies.
You need these. The science of how they work is fun to explore. Engage your inner nerd.