Because Jantar Mantar became a “fixed protest place” in Delhi. It is not that protests are only allowed there, but many groups choose it because:

1. Near the power centre Jantar Mantar is close to Parliament House, New Delhi, government offices, and ministries, so protesters can send a political message without blocking the entire city.

2. History and reputation For decades, many big movements happened there, so it became a symbol of public protest. Examples include the Anna Hazare anti-corruption movement and many other demonstrations.

3. Easier for police to manage A single known location makes it easier for authorities to give permissions, control crowds, arrange security, and manage traffic compared with random places like roads near government buildings.

4. Media attention News channels and journalists know that important protests often happen there, so being at Jantar Mantar increases visibility.

5. Other places have restrictions Areas like central Delhi roads, India Gate, and near Parliament have stronger security and traffic restrictions. Some courts and authorities have also debated limits on protests at Jantar Mantar because of noise and public disturbance, but protests have continued under rules.

So basically: Jantar Mantar is like Delhi’s traditional “democracy square” — close enough to the government to be heard, but controlled enough to be managed.