Why can't work hours be compensated both ways?

Our company has a rule of 8 hours are working everyday. Which is 40 hours a week. Fair, no questions asked

Sometimes when we come in late say 30 minutes, we are expected to compensate those 30 minutes as work within the week. Fair again.

When I work overtime for an 1 hour, and ask for 1 hour from next day, somehow it bothers everyone from HR to CEO Why is that fair? How is same rule not applying to everyone?