If the load is an open circuit, a 50 Ω power resistor can connect the open connection to electrical ground. If this resistor is not implemented, then the signal will bounce back and disturb the operation of the circuit. This resistor needs a large surface area in order to safely dissipate the power that has built up in the resistor. This also increases an inherent capacitance in the resistor which is dissipated with a built in inductive trace to pull the overall impedance as close to 50 Ω as possible.