If an element of the circuit is defective, the elements in the other branches can continue functioning because the current still flows through them.
The effect of each resistor is shared among the various pathways. The total resistance therefore drops instead of increasing as resistors are added.
Current intensity is shared among the various resistors, with the result that every time a resistor is added, the demand for current increases, as does the risk of an overload. It is therefore useful to install protective devices, such as fuses or circuit breakers, in this type of circuit.