Why do we wear Hijab during Salat?

I understand that we should wear hijab in front of others to cover our beauty, because we should be seen as our character, not our body. I know the criteria of hijab but I don't understand... Why do we also have to wear it during Salat, If I'm alone? If I stay in my room, and shut the door and curtains, no one will see me. what does it matter then that Allah (glory be to Him) can see me? even if I wear clothes, God Almighty can see all... Please not that **this** question (offered as duplicate) does not answer my question. I want to know why we wear hijab in front of God, not how to wear it.