Why does the discharge side of compressor theline returning to evap?

The discharge side of a compressor is connected to the expansion valve or other throttling device, not to the evaporator directly. The evaporator is at a low-pressure side of the refrigeration system, while the discharge side of the compressor is at high pressure. Hence, the refrigerant flows from the compressor discharge towards the expansion device, which controls the flow of the refrigerant into the evaporator.