Pat, the reason is that many of us have found that talking with the neighbor does nothing but cause more problems. My personal experience has been that the neighbors who are irresponsible about their dogs in the first place are unlikely to do anything about the problem, whether it be barking or wandering or whatever. The OP has said that he likes his neighbor and thinks that a second conversation will do the trick, and I hope it does. But I wasn't so lucky. I've finally decided to make no more comments to neighbors about problem dogs, but to just deal with it quietly myself, just as I would deal with a coyote causing problems.
I'm not talking about a dog that just comes by once in a while to say hello, but one that chases livestock or wildlife.