My guess is as food supplies began running low, domesticated animals like dogs and cats were the first to go. I am sure there were people who were hesitant about eating fluffy, but the need to survive would win out every time.
Plus dogs barking would be like babies crying. It's ringing the dinner bell for walkers.
Tis true. However, some well trained dogs are trained not to bark and to attack on command. They would be a valuable asset in protecting a group.