I don't pretend to be an expert on this in the slightest (nor on anything except James Bond

) and I'm sure you'll get many far more knowledgeable replies than this but there seem to be some areas of consensus, such as:
- Behavioural issues. Some male Dobes' behavioural issues improve if you lop their balls off. I think if I were a male Dobie and someone cut mine off I'd behave perfectly too, you never know what they might take next...
- Responsible breeding. Many here are very concerned about this. Breeding is a complex process these days and may feel the hit and miss 'oh maybe I'll breed from him, we'll see' attitude does not contribute a sincere effort to helping and improving the breed, in their eyes pretty much the only reason to do it. Having no balls automatically protects against the possibility of random productive one-night-stands.
- As already mentioned, the health issue, for both prostate and testicular cancer.
I'm sure there are many other pros and cons but from what I can work out, those are the main reasons.