hesistant to gallop in straight

Question
QUESTION: hello sir, may i know why few horses hesitant to gallop in the final straight even though it has a chance to win. in the below race report, the trainer hired one of the top jockeys to ride this filly which was declared the first favourite but finished second.

"Explanation of Jockey Suraj Narredu (RISE OF EMERALD) that his instructions were to go to the front or sit close 2nd which he had followed until entering the straight and thereafter when asked for an effort the filly did not raise a winning gallop inspite of his best efforts, noted."

ANSWER: HI--  SOME HORSES HAVE A ONE RUN RACE. IF YOU USE THEM TOO EARLY , THEN YOU HAVE NOTHING LEFT FOR THE FINISH OF THE RACE.  THANKS ED HESS

---------- FOLLOW-UP ----------

QUESTION: hello sir, may i know what do you mean by "one run race". the lay off between this horse's previous run and current run was 25 days. shes a 3 year old dark bay filly.

Answer
HI -- SOME HORSES ARE SPEED HORSES AND THAT IS ALL THEY CAN DO , AND THERE  ARE OTHER HORSES THAT ARE STRONG CLOSERS. IF YOU TRY TO CHANGE THE WAY THEY RUN , THEY WILL NOT PERFORM PROPERLY. SO A ONE RUN HORSE JUST HAS THAT ONE RUN IN A RACE. EITHER SPEED OR CLOSING. THANKS  ED HESS