A childhood belief about sport

As a small child I would sit with my mother to watch the afternoon horse racing on our T.V. She did not bet but took a very keen interest in form. Mother was nonplussed when I asked her why they made the poor horse named "Bar" run in every race. I felt it was no wonder his odds were so poor- the poor thing must have been exhausted. Not only was he in every race but he was at every meeting.
Mother obviously thought the joke too good to waste so did not explain that 20 to 1 bar is betting shorthand. I am embarrassed to say I was in my twenties before the penny dropped.