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.