And there are always many more waiting in the wings.
If that were only true... Tha maximum number of horses allowed in each of the Triple Crown races is 20. The Kentucky Derby had 20; the Preakness had 8; and the Belmont had 10. Not exactly banging down the door to get in or waiting in the wings.
No, only the Derby allows up to 20.
The others are more normal and allow only 14, which is gate capacity. Belmont is much wider than CD but sticks to the normal gate principle.