Clinton, how would you fly on groundspeed using steam driven instruments? Sure it could be done but not without you reaching for your wizz wheel. Everyone can fly on IAS and as 43Inches says airflow is IAS not groundspeed.
When there's a screaming northerly in Melbourne a jet might have a 300kt groundspeed on downwind and by the time they've rolled out on a 10 mile final it's back to 120kts. Alright, that's fairly extreme but it would be impossible to control using groundspeed. If both aircraft are flying more or less the same IAS profile they'll more or less be doing the same groundspeed at the same point, i.e. you have good idea what you're going to get.
I'd hand off a pair of 737s to approach with 12 miles at ARBEY both doing 280kts IAS into 250 IAS below A100 and they'd be a nice 5 miles as the front one touches down, untouched by the approach controller. With a screaming northerly you might need 15 miles at ARBEY to achieve the same result.