This is definitely not the case here, I agree with the other answers, this is a pretty bad PCB layout. However, in some cases it makes sense.
- When you are laying out logic and other ICs with fast transitions, or when some devices can consume enough power that trace widths become an issue, AND you are doing it in a two layer or single layer board or otherwise have no possibility of flowing proper planes for grounds and power in a particular section, THEN you would place a connecting grid of traces in which pins have multiple paths to each other.
That way you get as close as you can to having a plane and provide proper connectivity to avoid ground bounce, supply issues, and EMC problems. However, this is mostly limited to power and ground connections. I have seen what happens when inexperienced designers ignore this and see PCB traces as just ideal wires.
- In some cases, due to required component placement, there might be no
way to place a wide enough trace to handle a large current. THEN you
would provide multiple paths so as to accommodate the proper trace
- In some weird cases in which you can foresee a current through a trace magnetically inducing a potential on a trace on the other side of the board which can lead to problems. By laying loops with currents fields flowing in opposite directions with respect to the other trace you can reduce the induced field.
I know of an inexperienced designer who laid out a simple 2-layer board with an operational amplifier and made the mistake of placing the feedback components a few centimeters away from the inputs, leaving high-impedance signals at the mercy of induced fields from the other side of the PCB. His amplifier was a nice oscillator, I fixed it placing a thin wire across a different route.