"May I give your dog some treats?"
A lot of people, even dog owners, don't ask for permission to feed someone else's dogs. While they are probably acting out of kindness, they may not know that a dog they are feeding could have health issues, dietary restrictions, or is currently undergoing training that treats could interfere with.
That's why one should always ask for permission before giving treats to someone else's dog. Sometimes, just because you are doing something out of kindness doesn't mean it's the right thing to do.