More to the point, why do we still have the archaic 250kts below 10,000 ft law. Departures would be able to clean up and accelerate to a more ecconomical speed early, and get out of the terminal area a lot quicker, minimising noise.
Even more rediculous, the arrivals on their long dwnwind legs, speed having to be below 250 kts, more often than not with lots of flap out and engines at a much higher than idle setting. burning gobs more fuel and noise.
Why not allow them to wistle in at their best speed, around 300-320 kts, engines at idle like they used to. The noise level on the ground is noticeably less.
Heard all types of reasons, turning radius for sids and star, etc etc. Sounds more like official bulldust to me.