The primary selling point is availability. While sites like CoolMathGames sometimes get restricted depending on the district, DuckMath often slips through the cracks. It is optimized to run on networks with heavy restrictions, using mirror links and alternative domains to stay live.
Google Sites: Similar to GitHub, students often create clones of the DuckMath library on Google Sites to fly under the radar of IT departments. unblocked games duckmath link
While finding an unblocked link can be a fun challenge, it is important to remember why those blocks exist. To stay out of trouble: The primary selling point is availability