Adding overdrive, cost vs. benefits

[eXodus]

just watched a video about the newer 8 speed automatic from ZF. Here they are explaining that it is important to reduce how fast the gears are turning to reduce drag inside the transmission.
maybe thats why they take all gears into overdrive. ? my second guess that it's about torque, since the first two gears are torque multiplier an overdrive after the tranny has to be more heavy duty.