Why is Gregor Samsa in the book Metamoprhosis still known as Gregor even though he is a cockroach?

Answer 1

Because he's the only one who notices he's a cockroach, the story is pointing out that he's insignificant and doesn't matter, nobody notices him, regardless of his appearance.

Answer 2

Because the bug is still Gregor, even though as time goes on he loses more of himself.

Answer 3

I think even though he has mysteriously transformed into a gigantic insect on his bed one morning, his reaction is by means of thinking desperately from his worried mind. In other words, his mind and thought remain human reactions, it does not infer he is a total creature from such transformation.