Increased safety for children
Increased safety for other dogs
Increased safety for your dog as other dogs will fight with an intact dog
Increased trustworthiness (being able to allow the dog off leash)
Improved health as the chance for cancers, etc are reduced
Reduce your perceived liability in case of dog bite
Satisfaction of not contributing to dog overpopulation
And, realistically, for every puppy you produce another will be euthanized
Dogs should be at least two before breeding to clear for genetic defects
Increased mellowness
Smarter dog as a significant portion of brain power is freed up
Very few reputable boarding/training operations will take an intact dog
Intact males (or females in heat) are not welcome in any dog gatherings
Reduction in humping and licking of his and others' private parts
Better to have a stalwart companion than be in the livestock business