The answer to that headline question is depressingly simple: politics.
A new £1,000-a-year immigration skills levy is expected to be introduced on all firms for each skilled migrant they recruit from outside Europe, under a new crackdown ordered by the home secretary, Theresa May.
There is no sense to this at all. The point about accepting economic migrants is that doing so makes us richer. So why on earth we should be charging people for going through the process of making us richer is unknown. Except, of course, that we do know very well why this is happening.
There is concern generally about the level of immigration. We don't share that concern but then so what? Politics is the art of at least pretending to do something about the issues that the voters care about. But what can the government do about immigration?
It cannot limit any movement of people from within the European Union. Other than family reunion issues and the like the UK doesn't really have much in the way of unskilled ex-EU immigration. Refugees and asylum seekers are also dealt with under international agreements and are not part of domestic policy. The only part of immigration that is actually under the control of those in Westminster is skilled, economic, migration from outside the EU. Thus, if the populace are getting antsy about immigration that's where the people in Westminster will do something.
What they do, how they do it, the sense of what they do isn't the point at all. Given that something must be done and this is the only place where they can do something then this is where they will. Despite the fact that skilled migration is exactly the type we want and charging people for employing those who make us richer is simply nonsensical.
But then, you know, politics. It's rather why we're so adamant that politics should be restricted, as a way of running things, to only those things that cannot be handled in any other manner. Simply because the results from politics are so often so dismal.