> The candidate is certainly putting in more work than you are for that money, no?

No. I don't understand why they would have any claim on it. Typically when I interview, I'm looking forward to my potential salary. It wouldn't occur to me to try and take someone else's bonus.

> It’s a win-win for both parties.

It's not a win for me if I have to give away half of a bonus I earned. Or are you saying that a competitive salary isn't enough of a win for the referee?

I'm curious, how many times have you personally been involved in a transaction like this? You've given away referral bonuses? People have given their bonuses to you?