I would suspect most Indians/Pakistanis/Bangladeshis eat Indian at home on an almost daily basis. And why go out to a mediocre restaurant when you probably have much better food prepared fresh at home.

Also most of these places have the base ingredients already prepared and throw in chicken or lamb (as an example) according to orders. If any of you get the chance, try a home cooked meal at a South Asians house and it will be much nicer than the same dish at a restaurant.

But I do see plenty of younger Indians eating out at these places, but not so many of the older generation.

But the same can be said of British people. I eat British food most days at home but I still go out to British restaurants.