If my company has a referral bonus clearly I benefit financially in the short term from getting my own referral hired. That said, I'm genuinely not interested in referring people I wouldn't want to work with, so I'd be judicious in who I refer. But the question remains.
Even though I would not be interviewing my own referrals, I know what kinds of questions are likely to come up, and the personalities of the interviewers (my coworkers). None of this is particularly strategic or company secret information, per se, but it could give my referrals an advantage over an equally qualified "walk in" candidate.
I'm trying to decide if the fact that I already know the person and personally believe them to be a good choice for the job is sufficient to offset the possible unfairness of giving them another edge besides my recommendation (implicit in my referral).