Each night after we light the Hanukka candles we say "Haneirot Halalu" and we say
We kindle these lights [to commemorate] the saving acts, miracles and wonders which You have performed for our forefathers, in those days at this time, through Your holy priests. Throughout the eight days of Chanukah, these lights are sacred, and we are not permitted to make use of them, but only to look at them, in order to offer thanks and praise to Your great Name for Your miracles, for Your wonders and for Your salvations.
But in the Temple people used the light of the menora. Why are the hanukka lights so holy that we may not use the light (other than look at it)?