True- if there was a physical reason eg burst blood vessel, flipping palate or whatever, it’s in the punting public’s interest to know and also could help connections of the 3rd horse object to their horse’s new mark being handed out partly in relation to the two horses’ finishing positions.
It’s also annoying if you avoid backing a horse like Capeland next time out as you don’t know the reason for the bad run, then it goes and wins and the trainer says afterwards “oh yes he knocked himself and walked back to the stables a bit lame last time but he was as right as rain the next day” (Not saying that Nicholls does this after a win but some trainers do and it gets on my wick).