I believe the diffrence in opinions here is that pilots are only intreasted in the safety of thier flight and ATC of all flight. We don't ask just becouse we're curious we can really use any information given to improve saftey of the overall situation.
And i'll asure you that if the atc even have time to ask about the reason you are on a safe course and level.
however short answer you give just say anything that indicates 1. how serious it is and 2. what we can expect you to do. If you think my example was bad just say. "gear indication, stand by"
I.e. If someone tells me they got a gear issue I normally persume other flights will not be affected, that you in the best of all worlds whould like to climb a few thousand feet and get a safe course for 3-4 minutes, and that there will be sufficent time to prepare in case the PIC declares an emergency.