Well if it costs 15 dollars, then I fail to see the point of NOT getting one. Saving 15 dollars, or even “never been asked” does not really qualify in my view, when you are heading towards some uncharted territory (for you). Paperwork, and getting along with the officials can be a bitch in some places, the IDL is actually just a translation of the fact, that you hold a valid drivers license, definitely won´t do you any harm to have it with you, except maybe that you´re 15 dollars poorer. I actually remember that I have been asked to show it sometimes.
(But that´s just my 0.02 on the subject)