Wow, nice pictures! My kids are jealous of all the fun they're having.
Pat, don't know about your area, but around here I see a fair amount of people practice with collars on, especially puppies. Maybe not ones with big dangly stuff on them…lol, but still. Makes it easy to just grab dogs out of crates and walk them up to the field and go, no special equipment needed, and gives you something to catch them with afterwards. Also in race meets the dogs are allowed to run with collars on for easy grabbing at the finish line. Lots of folks do.
At lure trials in our neck of the woods, even for puppies, no one uses collars for practice…. correct that at race meets they all have collars..... I have seen how a collar can get caught in the line, not as much worry with a drag lure that they use for racing meets.
I usually run mine nekkid anyways, but never seen or heard of anyone having collar troubles around here. People use muzzles as well, which could cause the same potential problem I guess. I do use those now always.
Most of our oval races are continuous loop. But of course the straights are drag.