Because 20 minutes in an adoption room will tell all about a dog's potential compatibility. And, if you live in a rural area, it can be difficult to meet prior to delivery. The families will meet an animal based on an observed, careful decision from the foster and if the mismatch is apparent from the get go, will simply not leave the animal. But most mismatches can take over a week to see because the animal has behaviors surface only as it settles. Some puppies are very subdued and passive at first and then can change 180 in a new environment (especially as they are removed from the more aggressive and dominant litter mates).