Question for those with unaltered dogs...?

I see a lot of good dog owners on here that say they have unaltered dogs and are able to keep them from breeding. That's great that are able to keep them separated through heats to prevent unwanted litters but does the happiness of your dogs ever come into question? IMO, if I have a b^tch or dog that I never plan to show or breed it is the most humane thing to just have them fixed. Medical debates aside ( I think there are valid points on either side) what about the stress caused by having an unaltered male around a b^tch in heat? I could never do that to my dogs, male or female. I hate to see the desperation in a dogs face when they smell a b^tch in heat but are not allowed to breed and vise versa. What are your opinions on this? I am extremely attentive of my dogs, I have had unaltered rescues come through my home that were not yet fixed and it was heartbreaking to see them in such distress. What reason (health concerns aside) do you have to keep your dogs intact?