The reason I've been given was that the carb was mounted on the firewall, with the fuel going through the shaft and crankcase before entering the cylinders.
Were you to wait for the effect of a throttle change, you would have to wait until all the air between the carb and the cylinders had been exchanged. Controlling power with such a delay wouldn't have been good enough. Enter the blip throttle, which gave instant, if somewhat coarse, power control.
I guess this would have applied to later models than the Gnomes linked above - an interesting read for sure! "Hopefully" the mixture in the crank case did not ignite... oh geez!
Regards,
Fred