They are not, they are driven more into underground, the worship of Kali continues - it is an integral part of Hinduism. This is from the text above: "isolated cases of a Thug's proficiency with a noose still exist in India and in other parts of the world". They are isolated - ie harder to track.
The Thuggees have gone. Most of the forests where they thrived, in a small region of India, is gone. They aren't there. And they are certainly not an integral part of "Hinduism", if such a religion really exists as a united entity. Remember, deviants and crazies are there in every religion, but in a disproportionate fashion in Islam.
Surely they still exist too.