A) Just because we know something is genetic (via identical twin studies, for example) doesn't mean we know which parts of the genetic sequence are responsible

A) Just because we know something is genetic (via identical twin studies, for example) doesn't mean we know which parts of the genetic sequence are responsible B) There might be a constellation of genetic polymophisms involved, such that anything short of full-genome sequencing & analysis wouldn't yield anything useful C) Even the cheapest genetic tests are likely more expensive and take longer than a 15-minute behavioral test.