@Adham - On the newer Raspberry Pi OS / Debian, the system Python is marked as “externally managed”, so pip won’t install packages directly into it.
The recommended way is to use a virtual environment:
python3 -m venv depthai-venv
source depthai-venv/bin/activate
python -m pip install --upgrade pip
pip install depthai
Then run your DepthAI scripts from the same terminal (with the venv activated).