Well, imagine this situation: you want to drop net to tens of thousands; each major category -- workers, families and students -- is already pushing up at the limits; whom do you drop? Is that fair? Will it make the nation 'open to business and facing outwards' in the eyes of our nearest and most crucial allies and trade partners?
If less people leave in any given year than expected, would you damage the economy, disrupt families or arbitrarily increase income requirements to catch up? Would you simply nudge the quota up and up until it basically settles at the same level market demands, if so then what was the point of the extra administrative hassles, controls and expense when other things need the cash? And, just to add insult to injury, a swathe of economic projections from pension contributions to growth you have to rely on assumes 1 million arrivals as the baseline, or thereabouts.
Yeah. Rhetoric time!