The problem for employers is that trainees and interns are a risk; you need to screen them beforehand, and then you take a gamble about whether they'll get up to the required skill level in six months or a year to be up to par to the rest of the company's team.
I heard about a major consultancy company's success in attracting interns as potential future engineers (Ordina iirc), they said the success rate was about 1 in 20. Which, for smaller companies (<100 people) is simply not enough.
The article itself states they hired eight people from Hacker School, which is daring and commendable. I'm curious as to how those people will develop themselves in the coming year.