I guess you do not work in a TMA/busy environment.
Although this statement is not adressed to me, I DO work in a busy environment.
The busier it is the less one can afford to rely on performances based on non-specific clearances ("expedite climb").
I wanna know by when an aircraft can comply with a given rate, hence I give 'em a specific rate of climb/descent.
Being busy doesn't justify slack phraseology.