I always thought that one of the selling points for castration was that it prevented testicular cancer.
It is, and it's not necessarily going to happen - certainly we've had entire males forever (much as I spay my bitches, usually on retiring, I don't do castration other than for medical reasons!) either. Obviously if the testicle is retained, it needs to be removed (the risk of cancer for sure). 'Selling points' - you are not wrong.
Certainly there's a far greater risk, and it's still a risk, of mammary, ovarian or uterine cancers in an entire bitch later on. Although we've never had testicular cancer in our males, we have had one, in all our bitches over the years, who did develop mammary cancer when she was 12. Not nice.