So, OP originally asked why he/she needed one if he/she is not going to race.
My answer was that I don't have any use for it, but recognize that's only one possible answer.
So, I guess the question is, does the device have any use other than as a tool to train to go faster over distance?
@
doctorisotope mentioned he uses it as a fuel gauge, but isn't that really an endurance/racing issue? Honest question.