How do you know the other humans you interact with in real life are conscious? They might be biological automatons, golems. You will never know. It's not something that can ever be proven. Only human empathy allows anyone to believe otherwise.

You know you're conscious because your soul is staring out at the world through your eyes. Generalizing from your own experience and concluding that other humans are conscious is a logical jump, a spiritual belief. Humans even extend it to animals. There is no reason why it can't be extended to AIs.