IIRC it prompts you when you are on roaming (not on Sprint's network) if you wish to allow roaming data, or to allow a call you are making/receiving while roaming.
For the most part unless you are roaming all the time these features aren't needed, as it's unlikely you'll hit the 400MB roaming data limit, or the 50% call volume limit (less than half of your calls a month must be on roaming).
