Hi
One of the reasons could be that they disembarked in the Mediterranean. Ships coming through the Suez Canal would often call at a port such as Marseilles or Naples, some passengers preferred to then travel overland to a Channel port and cross on the ferry. I believe not only was this quicker but it avoided the sometimes rough weather in the Bay of Biscay.
Another thing I have noticed on Ancestry is that sometimes the index shows the port the ship originated from rather than where the passenger boarded (the image has the boarding port) so don't rule out ships that commenced from further east and called into India.
Andy
