There are some similar questions that have been asked, but I believe the nature of this situation is slightly more unique. I was recruiting for internship positions at multiple companies. I recently received an offer from a company which was my top choice. I had a few other on-site interview requests at other companies, but since I knew that I would not accept an offer from these other companies, I politely declined the interview out of respect of their recruiting resources. The recruiters received this well and even showed interest in maintaining contact for future opportunities (as this is just an internship).
However, after doing so, the recruiter of the company whose interview request I declined asked me the name of the company whose offer I accepted. I'm inclined to give them this information as I cannot see any reason why it could be detrimental. For context, since this is an internship, I'm not 100% sure that I don't want anything to do with these companies in the future (I'm still learning about the type of work/culture that is most suitable for me), so I do want to maintain a good relationship.
So my questions are: are there any cons to disclosing this information? Also, why would they be interested in this information in the first place (I can think of a couple reasons, but just want to hear some insights)?
Edit: I should also mention that this is an in-house recruiter.