You are correct in a way SUJ. However, I would venture a guess that at least
85% of the winning halter bred horses in today's market have Impressive in their bloodlines at least once. Working people don't want Impressive bred horses because there are so many out there that are built like halter horses and most of them cannot withstand a real horse's workload. Among non-halter people, Impressive has become a bit of a stigma, even if they are tested negative.
If the advertisements I have seen are any indication, breeders care little whether the horse is N/H or not. It's all about whether they have the muscles to win. Take Kid Clu for example; he has tested N/H but has still sired hundreds of colts. Kid Clu Quarter Horse
(you can click on "Reports" and select "Progeny" to see a list of his offspring)
And those are only the ones listed on ABP, I have no doubt that there are hundreds more.
Just like this. 5 of their advertised stallions are N/H (and there are a couple with no test status posted but they do have Impressive in their pedigree). Quarter Horse Halter Stallions...AQHA Stallions Page 1