Many rescues come from good homes where they were loved and cared for but were given up for reasons unrelated to the dogs themselves: divorce, work, distress or a death in the family and sometimes a move. Some of the rescue dogs do come from homes where they were neglected or even mistreated and some people didn’t realize the time that is needed with owning a Wheaten. And yes, some are given up due to behavioral problems. A rescue dog ready for adoption has lived with an experienced foster person who has evaluated the dog and determined it is ready for a forever home.
It is true that most rescue dogs have some baggage. Some of them have had tough start in life and did not come through it unscathed. But most people who adopt or work with rescue dogs believe that these animals know they are given a second chance and try hard to fit in their new environment.