The standard Indian takeout menu does not represent the kind of food eaten in India. India is a large country and "Real Indian food" is little more meaningful than "Real European food". Dishes commonly eaten in the North might be foreign to people living in the South and vice-versa. Takeout favourites (tikka masala, madras, rogan josh) don't exist in India in that form. Those dishes are European inventions inspired by Indian dishes.
When I open an Indian take-away menu I see chicken, beef, lamb, seafood and vegetarian dishes. But there is no pork. India is a predominately vegetarian country. When the modern take-out menu was invented, common European meats were added to the menu. Except for pork. How come?
The Chinese takeaway is a similar story. You will find chicken, beef, pork, seafood and vegetarian dishes that don't resemble anything eaten in China. Now we have pork but no lamb. I suspect that is because lamb is expensive in Europe. But it goes to show pork dishes sell. So why not pork Indian dishes?
Edit: Comments mention that Goan cuisine features pork from Portuegese influence. This is interesting because some dishes, for example Vindaloo, are an Indian take on a European dish, rather than for example Tikka Masala which is a European take on an Indian dish. However the question is only about the extent to which pork is eaten in India, insofar as it influences why pork never made its way onto Indian takeout menus in Europe.
Best Answer
In the UK you see lamb and chicken on "Indian" restaurant menus, but not beef or pork. I suspect that in the colonial era when the English wanted meat there were goats (near enough the same as sheep) and chickens because both are kept for food but not meat. So are cattle but they're special. There simply wouldn't have been a supply of pigs or the habit of rearing them - and English breeds brought by the colonists wouldn't do too well in the climate of much of India. Maintaining a supply of pork would have been hard. The English in India also used to exploit and increase religious divisions - at times and in places they relied on Muslims. Rumours of pig (and cow) fat being used as grease on rifle cartridges (which had to be bitten) were a factor in the rebellion of 1857, indicating the depth of feeling about forbidden food.
While many Indians are vegetarian, there are plenty who aren't, and that means there are plenty of dishes using the meats that are available.
Many if not most "Indian" restaurants in the UK are run by people of Pakistani or Bangladeshi heritage, who tend to be Muslims. This further explains the absence of pork as it's forbidden for Muslims (including just handling it I believe).
Goa is an exception in several ways. It was a Portuguese colony not a British one. Iberian pig breeds should tolerate the Indian climate better than British breeds. More importantly, Goa doesn't have a large Muslim population (8%, compare with the UK at 4%). Goa was ruled by the Portuguese before and during the Mughal empire, which had a huge influence on Islam in the rest of India.