The menorah in the Bais Hamikdash wasn’t about bringing in light, but rather about sharing the light of Kedusha-the Schena (Divine presence) to the rest of the world. Therefore, the window structure of the windows in the Bais Hamikdash were narrow from the interior and widened outward, indicative of this idea. Similarly, one of the molded designs on the menorah were cups, as opposed to a barrel, which is about retention. A cup signifies giving to another, pouring out, giving someone a drink to qunche his thirst. This message is perfectly in line with the entire theme of the Bais Hamikdash, especially the menorah.

לקו״ש כ״א