Interesting point, but there is a historical explanation for this. The Jews were originally a (linguistically) Canaanite people that worshipped the same pantheon as the rest of them, but over time they began to worship only their national God (similar to patron Saints, most polytheistic religions associate certain Gods with certain groups, like Athens and Athena in ancient Greece), Yahweh.
Yahweh was conflated first with the Semitic High God El (linguistically this is the same root as Arabic 'Allah,' though the Islamic 'Allah' retains only the name of the polytheistic deity, Latvians similarly call the Christian God 'Dievs' which was the name of their Pagan High God) to make him the most power of all deities, then finally the existence of other gods was outright denied.
At the time Moses issued the Ten Commandments the Jewish religion had yet to reach its monotheistic stage, and the existence of other Gods was not denied.
Yahweh was conflated first with the Semitic High God El (linguistically this is the same root as Arabic 'Allah,' though the Islamic 'Allah' retains only the name of the polytheistic deity, Latvians similarly call the Christian God 'Dievs' which was the name of their Pagan High God) to make him the most power of all deities, then finally the existence of other gods was outright denied.
At the time Moses issued the Ten Commandments the Jewish religion had yet to reach its monotheistic stage, and the existence of other Gods was not denied.
