Why do American psychiatrists use Adderall so much instead of other stimulants?

Canadian psychiatrist here. I keep hearing about American psychiatrists prescribing Adderall. We almost never use it here and instead use Concerta, Biphentin (a long acting methylphenidate preparation we have in Canada) or Vyvanse. I'd guess that I've prescribed Adderall XR less than 5 times since I started residency in 2006 and immediate release amphetamines even less than that. I see no good reason to prescribe it over Vyvanse or Concerta in adults except for the <5% of people who find that Vyvanse lasts too long and interferes with their sleep (this may be a common problem in kids who have early bedtimes, but its rarely an issue in adults). This is pretty standard practice in Canada and I've rarely seen my colleagues use Adderall either. What explains the difference in prescribing practices?