In order for them to fulfill this goal, they need to determine if the dog is good with kids, cats, other dogs, plays rough, jumps fences, has a high activity level, etc. The rescue group shouldbe able to provide you with an evaluation for each dog. The larger rescue groups may receive hundreds of adoption applications each month. Keep in mind that many of those applications will not be accepted. Just because someone applies to an adoption program, does not mean that they will automatically get to adopt an animal.
Most groups reserve the right to reject or deny any application for whatever reason.
It may be that you live in an apartment. It may be because you have small children. It may be because you travel extensively. Most likely, it may simply be that your philosophy on dog care differs from their own. Remember, most of these groups receive far more applications than they have animals available - they can afford to be extra particular about who adopts their animals.