This is a good question but first of all it is important to know that we see friends from the 11th and not from the 3rd house. However, Ketu sitting in the third house can deprive the happiness of friends because Ketu is a planet with separating tendencies. It is an introverted and reclusive planet, so it is one of its qualities to keep the person away from socialization.
More Information : - https://www.vinaybajrangi.com/blog/ketu-in-the-third-house/
