I don't know how many hundreds of LPC/OPCs that I have conducted in my time. It was not all that unusual to see a crew fly the G/A to the platform height with the gear still extended. I would say that in almost every case it involved the PNF forgetting to make the "positive rate" call and so the PF failed to call for "gear up". When pilots are very busy they can tend to act like one of Pavlov's dogs.