No-I think its just they aren't here in as great numbers because there isn't as much need for them. And , so, they really aren't going to make as much money. After all, they're businesses, right? The big bucks are in Iraq.
In most of Afghanistan the threat is quite low, and there is not much infrastructure, US or Afgh, to protect. The really "red" areas are largely confined to the east and southeast, along the Pakistan border, and perhaps (potentially...) Kabul. Incidents do occasionally occur outside these areas, but rarely. As well, Afgh has a functioning police and army, both of which appear to be doing much better than their Iraqi counterparts. For example, in the five months I have been here, I have never heard of a single attack on ANA or ANP recruits. In Iraq they are slaughtered fairly regularly.
Cheers