Why does God expect us to Obey Him?
Parents expect their children to obey them because parents have the right to be obeyed. Similarly a teacher expects his/her students to obey them. In the same way, God, who is our Creator, expects us to obey Him because He being the Creator deserves to be obeyed.
Vehicles work best with the oil, spare parts, tyre pressure etc. recommended by the vehicle manufacturer. We do not try to change it to our liking because we trust that the vehicle maker knows what is best for the vehicle. Similarly, our creator knows exactly what is good for us and has prescribed a way of life which is submission and obedience to Him.