Are you certain they do? You are addressing theists, not scripture.
What you reference is interpretation. Creation from nothing, or creatio ex nihilo, is theological interpretation. It isn’t necessarily Biblical. The doctrine developed later in Jewish and Christian thought.
The Bible does not declare creation from nothing, and in fact explicitly declares “with God nothing shall be impossible” in Luke 1:37.
At the most basic level God would be present during creation, God being eternal, and God certainly is not nothing or nonexistence.
Genesis 1:1 declares “In the beginning God created the heaven and the earth”. This proclaims the beginning of the heaven and the earth, the beginning of the universe, not necessarily the beginning of existence or creation from nothing. Again, at the very least God is present. God is not nonexistence.
Furthermore God is likened to a potter working with clay throughout scripture, specifically in verses such as Jeremiah 18:1-6 and Romans 9:21. This suggests God creates from phenomena existing, not from nothing or nonexistence.
Additionally Isaiah 45:18 states “For thus saith the Lord that created the heavens; God himself that formed the earth and made it; he hath established it, he created it not in vain, he formed it to be inhabited: I am the Lord; and there is none else”. Scripture further emphasizes forming and shaping, suggesting things already existent, not creation or beginning from nonexistence.
There is no explicit declaration of beginning from nonexistence in the Bible. In fact a common motif of formation and shaping from existent material is conveyed. God alone would be something, existence, not nothing or nonexistence.
What you reference is theological interpretation, not scripture.