1. Age: Some young male cats may be under-developed, resulting in incomplete exposure of Tintin.

2. Excessive hypertrophy of the yang sac: Too much fat in the yang sac may cover Tintin, so Tintin in the male cat will not be completely exposed.

3. Testicular ptosis: Male cats with testicular ptosis may lead to incomplete exposure of Tintin.

4. Protection: Many male cats will put away their tintin when they meet strange cats or dogs, because this can prevent them from being attacked.

5. Family status: Some male cats may think that they are the boss of the family or circle, so they will be more confident and powerful when facing their companions, and their tintin may be more prominent and obvious than usual.

In either case, if you notice that Tintin of your male cat has never been seen, you'd better consult a veterinarian. The vet can check your cat to make sure that he is healthy.