There are no good explanations for this tradition. There are however plenty of sermons and interpretations.
The Hasidic rebbe, Simcha Bunim of Peshischa, offers an answer. He discovers a beautiful lesson in the small letter alef. He teaches:
The letter alef is small just like Moses made himself small. Even though Moses attained the greatest heights ever reached by man, he was unmoved by that fact and remained as humble as ever. When a person stands at the top of a mountain, he does not boast about how tall he is, because it is the mountain that makes him so tall. By the same token, Moses felt that whatever he had accomplished was due to God, and he had no reason to feel proud of his achievements.
Imagine if the world had more people like Moses. Imagine if most people believed that all of their achievements were because of others. Imagine if we believed that our accomplishments and successes were because we are standing on a mountain top fashioned by God?
It’s an image worth pondering. It’s a world worth working towards.
It’s only because of others. It’s really only because of the mountain. Our achievements are because others lifted us.
On whose shoulders do we stand? To whom should we offer thanks?