[underlipton]

I'm not convinced they don't. If you look at Lyle's bib when he takes it off and shows it to everyone, there's something on the back. I thought it was another YuGiOh card at first, but then I thought, "That'd be the perfect place to put something to trigger some sort of check at the finish line."

[chedabob]

I suspect it's probably just easier for them to print all the race numbers the same way, but only use the transponder on races where it doesn't need to be accurate, or they need to take several measurements throughout the race.

For the longer distances, the lap times and finish times show up almost instantly when there's a big gap between athletes, although I believe there's a laser at the finish line too.