We do all of our own cases and I regularly used to do MAC for ERCPs. We did it that way throughout residency and I continued it into practice. Like most things we do, it's all about being selective in how you apply the tools you have at your disposal. If I'm working with one of my GI guys that I have known for 10+ years and it's a quick choledocholithiasis case that'll take him 10 minutes scope in to scope out, in a stable, normal body habitus patient, intubating them is unnecessary.
If you have a lineup of scopes, 5-10 minutes added onto each case to intubate, position the patient, extubate at the end, turnover the circuit, etc added onto each one leads to everyone getting home hours later. We have no swing shift, no relief, and we stay until the work is done. The point of doing MAC over GA in a particular case is the same reason why you probably don't preoxygenate every healthy patient for five minutes before induction - it's unnecessary in most cases and slows down your own day. However, if you have a bad looking airway in a morbidly obese patient, I can bet you will take your time to fill their FRC. Same thing here -if there is any concern either from the gastroenterologist side of things or the patient side of things, you intubate. Otherwise, MAC is a perfectly acceptable way of doing them.
I know you said you did it this way for years and one could argue it's not unreasonable so you know all this stuff, but I was just expanding on the reasons why you would choose to do it this way for those who have never done an ERCP under MAC before.