The fact that domestic cats cannot smell their mirror image is the reason why, it is said, they eventually become disinterested. Further, when a domestic cat looks in a mirror at themselves the mirror image does not emit any sound either.
These two important aspects of their mirror image eventually leads to them ignore it. Further, so far, science has failed to reveal any evidence for self-awareness in cats or even dogs. As the domestic cat is not self-aware and as their image moves but has no sound or smell, they may be interested in their image but it passes.
The movement of the image is probably what interests them. We see some domestic cats sparring with their mirror image in some sort of game. But all the videos that one sees on the Internet do not indicate that the cat is aware that they are looking at themselves.
When hunting, domestic cats rely upon movement and sounds (domestic cats can pinpoint prey accurately using sound). The cat’s eyes very sensitive to movement and we all know the sensitivity of the domestic cat’s nose. It is the reflection of their movement which interests the domestic cat when looking at himself in a mirror but it is not a sign of self-awareness.