There may be many reasons why a dog cannot escape. Here are some possible reasons:
Insufficient training: If the dog has not been trained, or is not trained enough, then it may not understand What you want it to do, or it may not react correctly.
The safety chain is too long: If your dog is on a safety chain and the chain is too long, he may have enough room to escape.
Safety chain is too short: If your dog is on a safety chain and the chain is too short, he may not have enough room to escape.
Environmental factors: Your dog may become trapped around a high fence, gate, or other obstacle that prevents him from escaping.
Health Reasons: If your dog is unwell or injured, he may not be able to escape.
Age factor: Older dogs may have difficulty moving due to age and are unable to escape.
Loyalty: For a dog that is loyal to its owner, it may not want to leave the owner's side.
Sociality: For a dog that likes to socialize with people, it may not want to leave the company of its family and other animals.