because you just get a overload of complete unknowns.
You get a large percentage that want to get a work visa and transfer thier licenses and think they are doing you a favour.
You then get a heap of folk that will apply anyway but have no interest what so ever about moving location. And even if they do they will get home sick when mummy doesn't tuck them up in bed with warm milk and does thier washing for them.
You then have a heap of FI's who have done the course but in reality they arn't suited to doing the job.
Then you have the very small amount that you would be interested in speaking to. Then its down to if thier personality fits.
Now even sifting through all the CV's will take alot of time, even more if you do the decent thing and reply to them.
Then there is the time wasters and incompetents you can't drag that out of them seeing them for 30 mins or more.
So the best bet is the opinion of someone you trust and knows the score and the knows the person over several weeks. Doesn't always work out mind. But you tend to get the right person without as much time and effort put in.
And to be honest other industrys are exactly the same with head hunting.