Slow adoption of transradial PCI in the US

We have determined that you must start out with trying ALL (appropriate) cases radial and the learning curve is about 50 cases. You should not cherry-pick your cases. Start out doing diagnostic and you can use the same catheters (left: JL 3.5 and right: JR4.0) of special catheters. Do not start doing STEMI cases of known PCI at first. Of course if the diagnostic turns into a PCI, we use XB 3.5, etc., guides. By 100 cases, you should be able to do the STEMI. Leave the LIMA cases alone from the right; not worth the work. Just go to the left radial.

Question: 

I am interested in exploring the reasons for the slow adoption of transradial PCI in the United States. I do appreciate that there is a steep learning curve to proficiency. If you could estimate or quantify gaining proficiency in terms of time and/or cost, I would be most appreciative. Thank you.